Prepare the peanut sauce by whisking together all ingredients except starchy pasta water in a small bowl. Set aside.
In a large skillet, sauté onion in sesame oil for 1-2 minutes.
Add carrots, garlic, and tomatoes; sauté for another 2 minutes.
Reduce heat, add broccoli, bell pepper, soy sauce, and lime juice. Sauté for 4-5 minutes until broccoli is bright green.
Boil ramen noodles until al dente, then strain, reserving 1/4 cup pasta water.
Combine noodles with veggies in the skillet.
Slowly whisk starchy pasta water into peanut sauce until smooth, then pour over noodles and veggies.
Toss until coated, then top with cilantro, green onions, peanuts, and sesame seeds.