Heat butter over medium heat in saucepan and saute onion until translucent.
Stir in rice and continue to cook until heated through.
Stir in spices, adjusting to your taste. (I like subtle flavors, so you might want to add extra.).
Cut tails off shrimp and cut shrimp into pieces. Turn pan down to low, then add shrimp and cheese, stirring until cheese is melted.
Assemble, making either 1 large or 2 small burritos. Add whatever extras you would like, such as avocado, tomatoes, shredded lettuce or cabbage, taco sauce, refried beans, sour cream -- or just leave it plain :).