Preheat the oven to 400°F. Grease a 9 x 13-inch baking pan with butter or coconut oil.
In a large nonstick skillet; cook the sausage, bell pepper, and onion until the sausage is cooked and the vegetables are tender, about 10 minutes. Drain off the fat.
In a large bowl; whisk together the flour, baking powder, herbs, and salt. Add the olive oil and buttermilk and stir gently, just until combined. Spread this mixture in the bottom of the prepared pan.
Spread the tomato sauce over the biscuit layer. Scatter the meat mixture over the tomato sauce. Sprinkle the cheese over the top.
Bake until the crust is crisp on the bottom and cooked through and the cheese is melted, 12 to 15 minutes.