One-Pan Weeknight Sausage and Peppers

In large skillet, heat 2 Tbsp olive oil over medium-high. Add onion; cook, stirring occasionally, until light golden, 5 minutes. Add bell peppers. Cook stirring occasionally until tender, 5 minutes. Add garlic, fennel seeds and red pepper flakes; cook, stirring occasionally until fragrant, 30 seconds. Salt and pepper to taste.