Make the crust: Combine the flour, cornmeal, and salt in a medium bowl, mixing until well combined. Cut the butter into very small pieces and mix in using your hands or two forks until mixture resembles coarse crumbs. Add the water, and mix until a cohesive ball of dough is formed. Wrap dough in plastic wrap and chill for at least 20 minutes before working it further.
Preheat oven to 375 degrees and line a baking sheet with parchment paper.
Combine the grated cheddar, cream cheese, scallions, dill, hot sauce, and black pepper in a bowl until well mixed. Check seasoning and add any salt if needed (the smoked cheddar I used was plenty salty, but this can vary between different cheeses).
Remove dough from the fridge and roll out on a well-floured surface until you have a large circle approximately 12 inches in diameter. Transfer dough to your lined baking sheet.
Spread half of the cheese mixture evenly into the center of the dough circle, leaving about a 3 inch border around the edges. Top with half of the sliced tomatoes, followed by the remaining cheese mixture, and the remaining tomatoes. (If you’re using cherry tomatoes, I recommend layering these on the top layer, as it will look prettier).
Fold up the edges of the dough around the filling, and sprinkle the top evenly with the parmesan cheese. Bake at 375 degrees until crust is golden brown and filling is bubbly, about 30 minutes.
Remove from oven, and sprinkle the evenly top with the fresh chopped chives and a couple of pinches of freshly ground black pepper. Cool slightly, then cut into slices and serve.