Preheat oven to 425°F.
Slice tomatoes into 1/2-inch slices.
Set out three bowls. In the first bowl, mix flour, 1 teaspoon of cornstarch, and cajun seasoning. In the second, mix egg, milk, and 1 teaspoon of salt. In the third, mix the panko, 1 teaspoon of salt, and 1 teaspoon of cornstarch.
Dredge each slice liberally in the flour mixture, then the milk mixture, then the panko mixture.
Place dredged slices on a baking sheet and place in the oven. Bake at 425°F for 12 minutes. Then, flip each slice and bake for an additional 12 minutes.