Slice tomatoes about 1/2″thick. Brush with mayonnaise. Sprinkle with salt & pepper.
Mix 1/3 cup each cornmeal & flour & 2 tbsp grated parmesan. Dredge tomatoes in mixture.
Drop 2 tbsp butter on rimmed baking sheet and melt in 450-degree oven. Place tomatoes on pan. Bake about 8 mins. per side or until golden.