1. Prepare the Cooking Environment

Heat the oven to 350F (175C) and coat a 9×5 inch loaf pan with non-stick cooking spray, ensuring complete coverage to prevent potential sticking.

1. Render Sausage Mixture

Crumble the sausage into a large skillet with finely chopped onions. Cook over medium heat, stirring continuously until the meat browns completely and loses its raw appearance. Drain excess grease on absorbent paper towels and allow the mixture to cool to room temperature.

1. Create Flavor Base

Whisk the egg in a spacious mixing bowl, incorporating Parmesan and cheddar cheeses. Introduce Texas Pete hot sauce, salt, and red pepper flakes, blending until the ingredients form a cohesive mixture.

1. Develop Bread Batter

Gradually integrate baking mix, milk, and mayonnaise into the cheese mixture. Stir methodically to eliminate potential lumps, creating a smooth, uniform batter.

1. Incorporate Meat Components

Fold the cooled sausage and onion mixture into the batter, ensuring even distribution throughout the mixture.

1. Bake to Perfection

Pour the prepared batter into the greased loaf pan. Slide into the preheated oven and bake for 45-50 minutes, monitoring for a rich golden-brown surface and checking doneness with a toothpick test.

1. Rest and Serve

Remove the bread from the oven and allow it to settle in the pan for 10 minutes. Carefully invert onto a cooling rack, slice, and serve while still warm to maximize flavor and texture.