Preheat oven to 400 degrees F.
Heat a stove-top grill pan or griddle to medium-high heat and coat with cooking spray. Season shrimp all over with salt, black pepper and cumin. Place shrimp on the hot pan and cook 2 minutes per side, until bright pink and cooked through. Place pineapple on grill next to shrimp and cook 2 minutes per side, until golden brown. Remove shrimp and pineapple from grill and cut both into 1-inch chunks.
Arrange 4 tortillas on a flat surface. Top with, shrimp, pineapple, cheese, red peppers, and scallions. Place second tortilla on top. Transfer with hands or with a spatula, to a baking sheet. Place a second baking sheet on top to weigh down the tortillas. Bake for 10 minutes, or until cheese is melted and tortillas are golden brown.
While the quesadillas are baking, in a small bowl, using a spoon, combine sour cream, lime zest and garlic. Mix well to combine.
In a food processor, combine mango and lime juice. Puree until smooth and remove from food processor and place in a bowl. Using a rubber spatula, stir in cilantro.
Remove quesadillas from the oven. Cut quesadillas into wedges and serve with lime sour cream and pureed mango on the side.