Preheat your oven to 350°F (175°C) and grease a 9x13 baking pan.

Melt 3 tablespoons of butter in a medium saucepan over medium heat, add diced red and green peppers, and sauté for 3-4 minutes until softened.

Stir in 1 teaspoon of oregano, 1 teaspoon of garlic salt, black pepper, and cayenne pepper, then add 2 tablespoons of flour and cook while stirring.

Gradually whisk in 2 cups of milk and stir until thickened, about 3-4 minutes.

Remove from heat and fold in 2 cups of shredded Mexican cheese and ½ cup of sour cream until melted.

Melt another tablespoon of butter in a skillet, add ½ cup of diced onion, sauté for 2-3 minutes, then add 1 pound of shrimp and cook until pink.

Gently fold in 1 cup of diced tomatoes into the shrimp mixture.

Spoon a generous portion of the shrimp mixture onto a tortilla, roll it tightly, and place seam-side down in the baking pan.

Pour the cheese sauce over the enchiladas and add more cheese on top if desired.

Bake in the oven for about 30 minutes until bubbly and golden brown.

Let the enchiladas cool for a few minutes before serving. Enjoy!