Preheat oven to 425°F (220°C).

In a large bowl, mix 1 1/4 cup flour, active dry yeast, and salt.

Add warm water and cooking oil and mix for 3 minutes.

Stir in 3/4 cup yellow corn meal and another 1 1/4 cup flour gradually until a dough forms.

Knead the dough for 6-8 minutes until smooth.

Divide the dough in half, cover, and let rest for 10 minutes.

Place each dough portion on a 13x11 inch baking sheet, pressing to extend dough 1 inch over the pan edge.

Roll the dough to form the crust.

Bake for 10-12 minutes, or until lightly golden.

In a large skillet, cook hamburger meat and chopped onion until the meat is browned.

Drain any excess grease.

Stir in tomato sauce and taco seasoning, heat through.

Spread the meat mixture evenly over the pre-baked pizza crust.

Sprinkle shredded cheese generously over the meat.

Bake until the cheese is melted and bubbly.

Remove from oven and top with shredded lettuce, chopped tomatoes, and chopped avocados.