Pre-heat the oven to 350 degrees.

Place 2 tablespoons of the butter in a large skillet over medium-high heat until melted. Add the onions and stir together. Cook for about 5 minutes until onions are softened and translucent. Add the garlic, a tablespoon of the basil and the cayenne pepper and stir together. Cook for an additional minute and then add the cubed large tomatoes, the brown sugar and the salt. Stir together until well combined. Wait until bubbling and then reduce heat to a simmer. Simmer for 4-5 minutes until tomatoes just begin to soften. Remove from heat and stir in the cherry tomatoes and the flour. Transfer the tomato mixture to a 2 QT baking dish. Cut the remaining tablespoon of butter into cubes and use them to dot the top of the tomatoes.

In a mixing bowl, combine the Bisquick mix, dry mustard, black pepper, the remaining teaspoon of basil, milk and shredded cheddar and stir until a soft dough forms. Use a spoon to drop pieces of the dough across the surface of the tomato mixture. Place the dish in the oven on the middle rack and bake for 35-45 minutes until the tomatoes are bubbly and the biscuit topping is golden brown. Let the dish rest and cool for 15-20 minutes before serving.