When a few breadcrumbs dropped in the oil sizzle, it's ready for frying! Fry fresh from the garden tomatoes, in batches, until golden brown and crispy. For a more powerful flavor, substitute blue cheese for feta.
Set a wire rack in a rimmed baking sheet. Place tomato slices on wire rack, and sprinkle with 1/2 teaspoon of the salt. Turn slices over, and sprinkle with another 1/2 teaspoon of the salt. Let stand 30 minutes. Blot tomatoes dry with paper towels.
Place flour in a shallow dish. Place eggs in a second shallow dish. Stir together cornmeal and breadcrumbs in a third shallow dish. Working with 1 slice at a time, dredge tomato slices in flour; dip in eggs, shaking off excess. Dredge slices in breadcrumb mixture, pressing gently to adhere. Place tomatoes in a single layer on wire rack.
Heat oil in a large, heavy skillet, preferably cast-iron, over medium-high. (When a few breadcrumbs dropped in the oil sizzle, it's ready for frying.) Fry tomatoes, in batches, until golden brown and crisp, turning halfway through, about 2 minutes per side. (Be careful not to overcrowd the skillet.) Transfer to wire rack to drain. Top each tomato with a pinch of salt.
Whisk together buttermilk, mayonnaise, sour cream, dill, and lemon juice in a small bowl. Whisk in black pepper, 1/2 cup of the feta, and remaining 1/4 teaspoon salt. Spoon about 3 tablespoons of the dressing onto each plate; add 3 or 4 tomato slices. Sprinkle with dill and remaining 1/2 cup feta.