Strain the pineapple juice from the can of pineapples into a large saucepan and reserve the fruit for later. Add the rice vinegar, vegetable oil, soy sauce, ginger, ketchup, honey, garlic, and cornstarch. Whisk to combine and cook over high heat for 10 minutes, or until the glaze is reduced by half and has the consistency of honey. Remove from the heat and divide the glaze in half.
Place the baby back ribs on a baking sheet and season with salt and pepper on both sides.
Brush half of the glaze all over the ribs.
Cover the ribs with aluminum foil, wrapping tightly.
Bake for 2 hours, or until the ribs are tender. Remove the ribs from the oven and increase the oven temperature to 400°F (200°C).
Remove the top piece of foil and add the red and green bell peppers to the baking sheet. Pour the reserved glaze over the top and toss to coat the peppers. Add the reserved pineapple over the ribs.
Bake for 20 minutes, until the peppers are softened.
Slice the ribs and garnish with sesame seeds and scallions. Serve warm with rice alongside.