Preheat Oven: Preheat your oven to 350°F (175°C). Don't forget to spray a 9x5 inch loaf pan with non-stick spray to ensure easy removal after baking.
Cook sausage and Onion: In a skillet, cook 1 lb. of crumbled sausage along with 1/4 cup of chopped onion over medium heat until the sausage is browned and the onions are translucent. Once cooked, drain excess grease and let the mixture cool for a few minutes.
Mix Ingredients: In a large mixing bowl, combine 1 egg, 1/4 cup of Parmesan cheese, 1/2 cup of grated cheddar cheese, 1/2 teaspoon of Texas Pete hot sauce, 1 teaspoon of salt, and a dash of red pepper flakes. Mix until well blended. Gradually stir in 2 cups of baking mix (Bisquick), 2/3 cup of milk, and 1/4 cup of mayonnaise until just incorporated.
Add sausage and Onion: Fold the cooled sausage and onion mixture into the batter until evenly distributed but do not overmix.
Bake: Pour the combined mixture into the prepared loaf pan. Bake in the preheated oven for 45-50 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Cool and Serve: Allow the bread to rest in the pan for about 10 minutes. Transfer to a wire rack to cool slightly before slicing. Enjoy your warm, delicious Sausage and Cheese Bread!