In Megilas Esther 7:4, Esther tells Achashveros that someone is planning on wiping out her people:
כִּי נִמְכַּרְנוּ אֲנִי וְעַמִּי, לְהַשְׁמִיד לַהֲרוֹג וּלְאַבֵּד; וְאִלּוּ לַעֲבָדִים וְלִשְׁפָחוֹת נִמְכַּרְנוּ, הֶחֱרַשְׁתִּי--כִּי אֵין הַצָּר שֹׁוֶה, בְּנֵזֶק הַמֶּלֶךְ.
for we are sold, I and my people, to be destroyed, to be slain, and to perish. But if we had been sold for bondmen and bondwomen, I had held my peace, for the adversary is not worthy that the king be endamaged.
None of this should be news to Achashverosh; Haman already told him about his plot to kill the Jews. The only new information here is that the queen herself is Jewish. So why does this information suddenly enrage Achashverosh against Haman? If anything, Esther was the one who withheld information. It's not even clear to me that Haman knew about Esther's relationship to Mordekhai and thus her Jewishness.