I got the idea for Mexican Pizza's from, Cheap, Fast, Good!, by Beverly Mills & Alicia Ross. Since trying their recipe I've adapted it to the likes of my family. The recipes contains only ingredients. You can decide on the quantity.
sour cream (optional)
Preheat the oven on a medium broil. Place the corn tortillas on a baking sheet and broil both sides of the corn tortilla just until crisp. About a minute and a 1/2 per side.
Meanwhile place about 1/2 cup of sour cream in an bowl and mix with 2 tsp. taco seasoning. Set aside.
Remove from oven and spread beans over corn tortilla, then sour cream mixture, salsa & cheese. Place pan in oven and brown until cheese melts. Watch closely so the edges of the corn tortilla don't burn.
Don't forget to check the labels of the products you are using carefully to make sure they are free of the allergens you are avoiding.
After removing from oven top with avocado and shredded lettuce. We cut the pizza for the kids in pizza wedges.