Cook spaghetti until al dente (tender cooked). Drain and set aside.
Cut pineapple chunks in half and set aside. Save ⅓ cup plus 1 tablespoon pineapple juice from can for peanut sauce. Toss the rest of the juice.
To make peanut sauce: In a small bowl, whisk together ⅓ cup plus 1 tablespoon pineapple juice, rice vinegar, peanut butter, soy sauce, water and red pepper flakes. Set aside.
Coat a large nonstick pan with cooking spray. Add oil, red bell peppers, scallions, ginger, garlic and ground turkey. Cook over medium-high heat, for about 5-6 minutes to brown the turkey. Be sure to stir often, breaking up turkey into small pieces, while browning. Cook until turkey is browned.
Stir in pineapple chunks and peanut sauce. Simmer, stirring often until sauce thickens, about 2 minutes. Taste the sauce, if you like it spicier, stir in a bit more red pepper flakes.
Leftover sauce will keep in refrigerator for a few days. The sauce tends to thicken when refrigerated so add about 1 tablespoon of water before heating. This sauce freezes great too!