First, prepare the dressing for the fish. Add the mustard, lime juice, and oil to a small bowl, season with salt the peppercorns, and mix well. Set aside.
Oil the grill, place the fish, zucchini, pepper, and onion, coat all with mustard-lime juice sauce, season with salt and pepper, and grill for about 15 minutes.
Brush the fish and the veggies again with the sauce, using the rosemary as a brush, turn them over, coat with sauce a third time, and grill for 15 minutes more.
Serve the fish and veggies garnished with lime, tiny tomatoes, and chopped basil leaves.
Notes
SIDE DISH RECOMMENDATION
If you’re looking for a side dish for this baked fish dish, a boiled potato salad would be lovely. You can dress your potato salad with extra virgin olive oil, lime juice, and mustard and season it with salt and pepper.