Preheat oven to 400°F. Grease a 12-cup muffin tin or line with paper liners if desired.
In a large bowl whisk together flour, cornmeal, sugar, baking powder, and salt. Make a well in the flour mixture and add egg, oil, and milk. Stir until just combined and the batter is moistened, being careful not to over-mix.
Divide the batter evenly among the muffin tin cups. Bake for 12 to 14 minutes or until lightly golden. Remove from oven.
Meanwhile, in a medium bowl, combine tomatoes, bell pepper, cucumber, scallions, basil, parsley, balsamic vinegar, olive oil, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Toss until evenly coated.
To serve, cut each cake in half lengthwise. Spread 1 tablespoon sour cream on each half. Place one half on a plate and top with some Balsamic Tomato Salad. Add another cake half with sour cream, then top with additional salad.
Repeat with remaining cakes and salad. Serves 6 as a main course or 12 as an appetizer.