Heat the oven to 500 degrees.
Halve the potatoes lengthwise, then cut each half into 5 wedges. Place the potatoes on a baking sheet and drizzle with about 3 tablespoons of the olive oil. Add the crushed garlic to the potatoes and sprinkle with the rosemary; season with salt and pepper. Toss the potatoes and garlic to evenly coat in the olive oil and seasonings, then roast for 25 minutes or until tender and golden at the edges.
Once the potatoes have cooked for about 12 minutes, heat the remaining 1/4 cup of extra-virgin olive oil in a skillet over medium-high heat. Season the fish with salt and pepper.
Combine the cornmeal, flour, cheese and the lemon zest on a plate, and coat the fish evenly. Add the fish to the skillet skin side up and cook until deeply golden brown on both sides, turning occasionally, about 8 minutes total.
While the fish cooks combine the tomatoes, parsley, scallions, lemon juice and a drizzle of olive oil in a small bowl. Season the sauce with salt and pepper to taste.
Serve the fish with a little of the sauce on top and with the potatoes alongside.