Preheat broiler to HIGH with oven rack 6 inches from heat.
Heat a grill pan over medium-high. Slice pineapple into 8 (1/2-inch) rounds. Using 1 ½ tablespoons of the oil, brush oil on both sides of pineapple rounds. Working in batches, place pineapple rounds on grill pan, and cook, 3 minutes on each side, until char marks appear. Transfer to a rimmed baking sheet.
Place Canadian bacon slices on grill pan and cook, 1 to 2 minutes on each side, until heated through. Set aside.
Heat remaining 1 ½ teaspoons oil in a separate nonstick skillet over medium. Add onion and cook, 3 to 4 minutes, stirring often, until softened.
Top each pineapple round with 1 tsp. cheese. Place 1 slice Canadian bacon on top of cheese. Top each with 1 tablespoon pizza sauce and 1 tablespoon cheese. Top evenly with onion and black olives. Broil on HIGH for 2 to 3 minutes, until cheese is bubbly and melted. Sprinkle basil and crushed red pepper flakes evenly overtop.