Begin by gathering all your ingredients and preheating your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.

Press the biscuit dough evenly into the bottom of the dish, ensuring it reaches about halfway up the sides. Place in the oven and bake until the dough is lightly golden, which should take around 15 to 20 minutes. Keep the oven on after removing the pan.

In the meantime, heat a nonstick skillet over medium-high heat. Add the ground beef and cook, breaking it apart until it's browned and crumbly, about 5 minutes. Drain any excess fat. Stir in the taco seasoning along with the water. Bring the mixture to a boil, reduce the heat, and allow it to simmer for 5 minutes while stirring occasionally. Once done, transfer the beef mixture to a bowl and set it aside.

Using the same skillet, add the sliced onions and bell peppers. Sauté over medium heat until they begin to soften, roughly 5 minutes.

In a separate bowl, mix together the sour cream, mayonnaise, half of the shredded Cheddar cheese, and half of the sautéed onion-pepper mixture.

To assemble the casserole, layer the cooked beef on top of the pre-baked biscuit crust. Follow with slices of tomatoes, the remaining sautéed onion-pepper mixture, and optional jalapeño peppers. Spoon the sour cream mixture over the top, spreading it evenly. Sprinkle the remaining Cheddar cheese over everything.

Return the dish to the oven and bake, uncovered, for 30 to 40 minutes, or until the cheese has melted and turns bubbly and golden. Let the casserole cool slightly before serving.