Pour the vegetable oil (1 teaspoon per bowl) into medium (1.2 quart) oven-proof bowls and rub around to coat the surface. Press each tortilla into a greased bowl.
Bake for about 10 minutes, until golden brown. Let the tortilla bowls cool.
Make 3 cuts lengthwise on each of the romaine hearts, remove the stems, and chop into smaller pieces. Rinse, drain, and place in a large salad bowl.
Dice the tomatoes and add them to the bowl with the romaine.
Dice the onion and add it to the salad.
Cut the avocados in half, remove the pits, and dice. Add to the salad.
Add the corn and black beans.
In a small bowl or liquid measuring cup, combine the olive oil, lime juice, garlic, cumin, red pepper flakes, cilantro, salt, and pepper. Mix well.