Preheat your oven to 350°F (175°C). Grease a 9x5 inch loaf pan with cooking spray or butter.

In a skillet over medium heat, crumble and cook the pork sausage with the chopped onion until golden brown, about 8-10 minutes. Drain excess fat and set aside to cool.

In a large mixing bowl, crack one egg and add the grated cheddar cheese, Parmesan cheese, Texas Pete hot sauce, salt, and red pepper flakes. Mix well until combined.

Gently stir in the Bisquick baking mix, milk, and mayonnaise until just incorporated. Fold in the cooled sausage and onion mixture.

Pour the batter into the prepared loaf pan and bake for 45-50 minutes until golden brown and a toothpick inserted comes out clean.

Cool in the pan for 10 minutes before turning it out onto a plate. Slice and serve warm.