On a large plate, pour the red sauce over the shrimp and set aside.
Heat a large skillet over medium-high heat and add the olive oil. Cook the onions and bell peppers over high heat until they start to get nicely browned.
Stir them after a minute or so, then let them sit on medium-high heat until they're nice and brown.
Add the pineapple and cook over medium-high heat until they start to get brown/black. Remove from skillet and set aside.
Add the shrimp and cook, stirring only occasionally, until the shrimp are opaque. Add in a little water if the sauce gets dry. Remove from the skillet and chop the shrimp into bite-size pieces.
In a clean skillet, heat some butter. Place a tortilla in the skillet, then layer on the ingredients: cheese, vegetables and shrimp. Top with a little more cheese and a second tortilla. Cook on both sides, adding butter before flipping to the other side so the tortilla isn't overly dry. Remove from the skillet and slice into wedges. Repeat with the rest of the tortillas and filling ingredients.
Remove the quesadilla from the skillet and slice it into 4 wedges using a large pizza cutter.
Serve the quesadilla with pico de gallo, guacamole and sour cream.