Combine 1/3 cup oil, juice, soy sauce, cumin, oregano, cayenne and garlic in an 8-inch dish. Add tempeh, tossing to coat. Cover, and refrigerate 2-12 hours, stirring occasionally.
Heat a large cast-iron grill pan over medium-high heat. Brush pan with oil. Add half of tempeh to pan. Cook 5 minutes on each side,transfer to a bowl, and cover to keep warm. Repeat with remaining tempeh.
While tempeh cooks, toss onion and bell pepper with remaining 1 tablespoon oil, salt and black pepper. After tempeh is done, add bell pepper mixture to pan. Cook 5 minutes, or until tender.
Heat tortillas directly over the flame of a gas stove or in a dry nonstick pan. Place 2 tortillas on each of 4 plates. Top evenly with tempeh and bell pepper mixture.