Cook onion in oil in a small saucepan for 3 minutes. Remove from heat; stir in crabmeat, mayonnaise or salad dressing, chili pepper, and cheese. Spread half of the filling on half of one tortilla. Fold the tortilla in half; set aside. Repeat with remaining filling and tortilla.
Melt butter or margarine in a large skillet over medium heat. Add the tortillas and cook, uncovered, for 2 to 3 minutes, turning once, or till golden brown on both sides. To serve, cut each quesadilla into four pieces. Serve with Pineapple Salsa. Makes 6 servings.
Stir together pineapple, red sweet pepper, cilantro, green onion, sambal or Chinese chili sauce, and brown sugar. Makes about 1 cup.