Thoroughly rinse produce and pat dry. Peel and cut onion into small 1/4" dice. Cut tomatoes into small 1/4" dice. Cut lettuce into shreds.

Heat a medium pan over medium heat. Add 1 tsp. olive oil, beef, half the onion, and Southwest seasoning. Cook until beef is browned and no pink remains, about 5-8 minutes. Add refried beans and 1/4 cup water to pan and cook until water has been absorbed and beans are evenly distributed, about 2-3 minutes. Texture should be somewhat thick. Season to taste with salt and pepper and set aside.

Heat red and green sauces in two separate small pots over medium heat until warmed through, about 2-3 minutes. (In a pinch, you can microwave these in two small bowls on medium power for 1-2 minutes.) Season both sauces to taste with salt and pepper.

Wrap 2 tortillas in a clean dish towel and microwave until soft and pliable, about 1 minute. Fill tortillas evenly with beef filling, remaining onion (to taste), 1/3 of the cheese, 1/3 of the tomatoes, and 1/3 of the lettuce per burrito.

Fold sides of tortillas over filling. Then, fold bottoms of tortillas over sides and filling and roll tightly. Roll tightly, but not so tightly that the filling gets squeezed out. Cut burritos in half.

Spoon half the red and green sauces on opposite sides of a plate. Arrange remaining lettuce and tomatoes in the middle of the plate and rest the burrito halves on top. Spoon remaining red and green sauces over the burritos and garnish with sour cream and remaining cheese.