Mexican Seafood Salad

2 tablespoons vegetable oil, divided
1 tablespoon lemon juice
1 teaspoon ground cumin
1/2 teaspoon chili powder
1 clove garlic, minced
1-1/2 pound medium shrimp, shelled and deveined, or scallops,
or a firm-textured fish, cut into1-inch chunks
1 large onion, halved lengthwise and thinly sliced
1 large red bell pepper, stemmed, cored and thinly sliced
6 flour tortillas, warmed
6 tablespoons prepared salsa, plus additional for serving
4-1/2 cups finely shredded iceberg lettuce, (1 medium head)
1 large avocado, peeled and thinly sliced

Combine 1 tablespoon oil, lemon juice, cumin, chili powder and garlic in a medium bowl. Stir in seafood and marinate 20 minutes, stirring occasionally. Heat remaining 1 tablespoon oil in a large skillet over medium-high heat. Saute onion and red pepper until tender but not brown, about 5 minutes. Add seafood with marinade and continue to cook for about 4 minutes. Set aside. Spread each tortilla with 1 tablespoon salsa and divide lettuce equally over the top. Spoon warm seafood mixture over lettuce and garnish with avocado slices. Serve with additional salsa.