Heat 2 tsp canola oil in a large sauté pan over medium heat. Add onions and jalapeño and sauté for 4-5 minutes, stirring occasionally, until softened. Add chili powder and cook for additional 30 seconds. Add corn and salt and cook for an additional 2 minutes.
Transfer corn mixture into a bowl, add mayonnaise and lime juice and stir until combined.
Heat large frying pan over medium heat. Brush pan with a tsp of oil. Lay one tortilla in pan and top ½ with ¼ of corn mixture, and sprinkle with ¼ of grated cheese. Fold tortilla over to make a half-moon and press down on top half with a spatula.
Cook quesadilla for about 2 minutes, carefully flip it over and cook an additional 2 minutes until tortilla is browned and cheese is melted. Transfer to a cooling rack then cut into 3 pieces when slightly cooled. Repeat with remaining 3 tortillas.
Serve plain or with salsa and/or sour cream, if desired.