Heat the vegetable oil in a large skillet or pan over medium heat. Add the chopped onion and cook until softened, about 3-4 minutes.
Stir in the minced garlic and grated ginger, and cook for another minute until fragrant.
Add the red curry paste to the skillet and cook, stirring constantly, for about 1 minute to toast the spices.
Pour in the coconut milk and vegetable or chicken broth, stirring to combine. Bring the mixture to a simmer and let it cook for 5 minutes to allow the flavors to meld.
Add the sliced bell peppers and cherry tomatoes to the skillet. Cook for an additional 3-4 minutes, or until the vegetables are just tender.
Stir in the shrimp and cook for 3-4 minutes, or until they are pink and opaque.
If using, add the fish sauce and brown sugar or honey to the curry, and season with salt and pepper to taste.
Once the shrimp are cooked through and the sauce has thickened slightly, remove the skillet from the heat.
Serve the Coconut Curry Shrimp hot over cooked rice or with naan bread. Garnish with fresh cilantro leaves and serve immediately.