01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish.
02 - Cook sausage in a large skillet over medium heat until browned and cooked through, breaking it up with a spoon. Drain excess fat.
03 - Add diced onion and red bell pepper to the skillet; sauté for 3 to 4 minutes until softened. Stir in spinach and cook until wilted, about 1 minute. Remove from heat.
04 - In a large bowl, whisk together eggs, milk, salt, black pepper, garlic powder, and paprika until combined.
05 - Spread cubed bread evenly in the prepared baking dish. Top with the sausage and vegetable mixture, then sprinkle shredded cheddar cheese evenly over all.
06 - Pour the egg mixture evenly over the layered ingredients, pressing down gently to help the bread absorb the liquid.
07 - Bake uncovered for 40 to 45 minutes until the center is set and the top is golden brown.
08 - Allow to cool for 5 to 10 minutes. Garnish with fresh herbs if desired. Slice and serve warm.