Mix cottage cheese, Monterey Jack cheese, tomatoes, onion, and taco seasoning mix and set aside.
Place tortillas on a microwave safe plate.
Cover with waxed paper and microwave on medium power (5) for 1 minute, or until warm and softened.
Spoon about 1/3 c. of the cheese mixture onto each tortilla.
Roll tortillas and place seam side down in a shallow casserole.
Pour salsa over enchiladas.
Cover with vented plastic wrap and microwave on medium-high power (8) 3-4 minutes, or until hot. Rotate halfway through cooking period.
Sprinkle with shredded Colby cheese.
Microwave uncovered on high 1 minute until cheese is melted.
Top with sour cream if desired.