Combine breadcrumbs, flour, cornmeal, parmesan, and dried basil in a small bowl. Slice tomatoes.
Roll pie dough out until it's about 1/4 inch thick. Cut out 5-6 inch rounds or squares (I like to trace a tupperware lid to make the rounds). Alternatively, you could make one large galette.
Spoon about 1-2 tablespoons of breadcrumb mixture onto each pie dough round, smoothing it out and leaving some space around the edges where you'll fold the dough up. Place slices of tomato on top and sprinkle with salt and pepper.
Fold dough up around edges, creating a pie dough border. Brush with egg wash and sprinkle edges with more parmesan.
Freeze galettes for 20-30 minutes, until chilled and firm - this will help them hold their shape when they bake.
Preheat oven to 375° F. Bake tarts until crust is golden and tomatoes are bubbling, about 30-35 minutes. Allow to cool for a few minutes; sprinkle with fresh basil.