Gemara

(Rav Chisda): If a Neveilah became mixed with a majority of Shechutos (slaughtered animals), it is Batel, for a Shechutah cannot become (an Av ha'Tum'ah, like) a Neveilah. If a Shechutah became mixed with a Neveilah, it is not Batel, for a Neveilah (when it rots) can become like a Shechutah (this is like Min b'Mino).

(R. Chanina): If the Batel (minority) can become like the Mevatel (majority), it is not Batel. If the Batel cannot become like the Mevatel, it is Batel.

(Beraisa): If Matzah was seasoned with Ketzach (black cumin) or sesame or other spices, it is Kosher, for it is (still) Matzah, just it is called seasoned Matzah.

We are thinking that the spices are the majority.

Question: We understand according to R. Chanina. Since the Batel (Matzah) can become like the Mevatel (spices), when it will become moldy (it will lose the status of Matzah), it is not Batel;

However, according to Rav Chisda, since the Mevatel cannot become like the Batel, there should be Bitul!

Answer: The case is, the Matzah is the majority, and not the spices.

Support: (Beraisa): It is Matzah, just it is called seasoned Matzah.

Zevachim 78a (Mishnah): If a dough was made with wheat flour and rice flour, if the wheat can be tasted, Chalah must be taken, even if the rice is the majority.

If it was baked into Matzos, one is Yotzei with it (for Matzas Mitzvah one may not Seder night).

Rishonim

Rambam (Hilchos Chametz 5:20): One may put spices, sesame, Ketzach and similar things in the dough. Similarly, one may knead the dough with water (Magid Mishneh's text - wine) and oil or honey or milk, or to wet it with them. On the first night one may use only water, not due to Chametz, rather, in order that it will be "Lechem Oni." Only on the first day we must commemorate Lechem Oni.

Kolbo (48 DH Ein Nosnim): One may put spices, sesame, Ketzach and similar things in the dough. It seems that the Rambam permits seasoned Matzah. This is the custom; also Tosfos says so. The Ra'avad (Tamim De'im 27) says that we do not put salt or spices in the dough, for they are like Rose'ach (boiling).

Rambam (6:5): One is Yotzei with Matzah kneaded with Mei Peros.

Rebuttal (Ra'avad): A Tosefta (2:13) says that one is Yotzei with Matzah seasoned in a pot or frying pan. This refers to Matzah seasoned after it was baked.

Magid Mishneh: It seems that the Tosefta is like R. Yosi ha'Glili, who expounds "Lechem Oni" to exclude Ma'aser Sheni, but not Matzah kneaded with wine or oil. Therefore, it permits Matzah Ashirah. The Halachah follows R. Akiva, who forbids Matzah Ashirah. It is difficult to say that the Tosefta discusses Matzah seasoned after it was baked, like the Ra'avad says.

Beis Yosef (OC 455 DH Garsinan): In any case we learn from the Tosefta that spices do not ferment. (Even R. Akiva forbids only due to Lechem Oni.)

Rosh (Pesachim 2:23): The Roke'ach (283) says that Matzah seasoned with Ketzach, sesame or all kinds of spices is Kosher, since it has the taste of Matzah. In any case one should not put in peppers, for they are sharp and they warm the dough.

Mordechai (Pesachim 594): The Ri permits putting spices in the dough, like it says in Menachos. Also the Rambam permits l'Chatchilah.

Tosfos (23b DH Ela): Why does our Gemara compare Matzah with spices, which have different tastes, to Neveilah mixed with Shechutah, in which the tastes are the same? Since the spices get the taste of Matzah, one should be Yotzei through them, like one must take Chalah from a dough of wheat and rice that has the taste of grain (Zevachim 78a)! We must say that our Sugya disagrees. Pesachim 115a says that one should not eat Matzah and Maror together, lest Maror, which is only a Mitzvah mid'Rabanan nowadays, Mevatel Matzah. There, the bitterness of Maror is Mevatel the taste of Matzah. Rice is not Mevatel the taste of wheat. Also, we can say that when one eats only a k'Zayis of Matzah, the Maror is Mevatel it, but not if one eats much Matzah.

Tosfos (Beitzah 14a DH Beis Hillel): Our Gemara permits grinding spices, but Shabbos 141a permits only one pepper at a time with the back of a knife! A Tosefta (1:12) says that peppers are like spices! We must say that the Tosefta equates them regarding Shabbos, but they are different regarding Yom Tov.

Gra (DH u'Pilpelin): Peppers are not called spices, like Tosfos (Beitzah 14a) says. We find that peppers heat (it can cause a woman to become Nidah - Nidah 63b).

Poskim

Shulchan Aruch (OC 455:6): If one kneaded Matzah with Ketzach, sesame or spices, it is Kosher, since it has the taste of Matzah. In any case one should not put in spices, for they are sharp and they warm the dough.

Bach (12): It is Kosher for the Mitzvah. It seems that the Roke'ach does not distinguish peppers from other spices. He said 'all other spices' (are permitted)! Rather, he explains the Beraisa. The Beraisa says 'if one spiced', which connotes b'Di'eved. The Roke'ach mentioned peppers, for it is common to put them in a douigh or cooked food; the same applies to other spices. R. Yerucham explicitly says in the name of the Roke'ach that one may not put spices in the dough. However, the Mordechai and Rambam permit spices l'Chatchilah. Alternatively, there is no argument. The Roke'ach forbids only peppers, and even b'Di'eved, because they are sharp and warm the dough. When there is concern for Chimutz, we do not distinguish l'Chatchilah from b'Di'eved. Chagigah 10a says that one sharp pepper (is better than a barrel full of gourds). The Aruch (Erech Pilpel) says that pepper is stronger than all spices. Also the Roke'ach permits other spices l'Chatchilah. It seems that the Ri and Rambam permit only spices, but not peppers. However, the Beis Yosef ruled that one may not put spices in, for they are sharp and they warm the dough. He holds like my first Perush, which distinguishes only l'Chatchilah from b'Di'eved, but not peppers from other spices. The Kolbo, citing the Ra'avad, forbids all spices. This is the custom; one may not breach the fence. According to the Ra'avad, even b'Di'eved one is not Yotzei. The Roke'ach rules like this.

Magen Avraham (17): One must eat a k'Zayis of Matzah without the spices.

Magen Avraham (18): The Shulchan Aruch connotes that one is Yotzei with it, but the Rambam and Magid Mishneh say that it is Matzah Ashirah.

Gra (DH Kivan): Tosfos says that our Sugya argues with Zevachim 78a. We hold like the Sugya there, for one is liable for a mixture of Isur Min b'Eino Mino if it gives taste. This is why the Shulchan Aruch says that it depends on taste.

Gra (DH umi'Kol): The Yerushalmi connotes unlike the Ra'avad. It says that liquid may not come on the k'Zayis of Matzas Mitzvah. It asked from the Beraisa that says that one is Yotzei with seasoned Matzah even if it does not have the taste of Matzah, as long as it is mostly grain. It suggested that it is seasoned with liquids, and answered that it is seasoned with sesame or nuts. This shows that one is Yotzei even if it was seasoned before baking, for Matzah Ashirah does not apply after baking.

Mishnah Berurah (45): The Shulchan Aruch connotes that it suffices of there is a k'Zayis of grain within Kdei Achilas Pras of Matzah. The Pri Chodosh and Magen Avraham connote that one must eat enough Matzah so that he eats a k'Zayis of grain without the spices. Regarding a mixture, l'Chatchilah we require that the majority is grain. The same applies here,

Mishnah Berurah (46): The Shulchan Aruch connotes that one is Yotzei with seasoned Matzah on the first night, therefore, one may not eat it on Erev Pesach. However, some say that it is Kosher only for other days, for it does not become Chametz, but it is Matzah Ashirah. One should be stringent.

Kaf ha'Chayim (103): If it was seasoned after baking, one is Yotzei with it. If it was kneaded with wine, oil or honey after baking, even though it is not Matzah Ashirah, it does not have the taste of Matzah. It is no better than Matzah soaked in Mei Peros; one is not Yotzei with it.

Rema: If one put in peppers, even b'Di'eved it is forbidden. The same applies if Sid (lime) fell in.

Magen Avraham (19): Even one stick of pepper makes the entire dough Chametz. The same applies to Sid. I say that this is only if it was kneaded with it, but if it merely fell in, one removes it, and it is permitted. Kitzur Piskei ha'Rosh connotes that it is permitted b'Di'eved, but one should not be lenient. See what I wrote in Sa'if 5 (if` a grain of salt fell in the dough, it should be baked immediately. We may rely on the Kolbo, who says that a small amount of salt does not warm.)

Gra (DH v'Chen): Shabbos 47b and Bava Basra 17a show that Sid warms.

Mishnah Berurah (49): Some say that if it was kneaded with any spices other than peppers or Sid, b'Di'eved one may eat it.

Mishnah Berurah (50): This refers to raw Sid. Surely we do not forbid due to Sid that was in a wall, which has already dried like a rock.

Kaf ha'Chayim (107): B'Di'eved, one may leave it until after Pesach (and eat it).

Kaf ha'Chayim (108): If it was kneaded only with Mei Peros without water, even if peppers were added it is permitted.

Kaf ha'Chayim (111): R. Zalman permits mixing Ketzach, sesame and other Zera'im (that are not sharp) in the dough, as long as they are ground up, for some say that small things impede baking. The Levush says that Ketzach is sharp.