In a shallow bowl, combine the cornmeal and chili powder; season with salt and pepper. Lightly coat each piece of fish with the mixture.
In a large nonstick skillet, heat 3 tablespoons olive oil over medium heat. Working in batches, add the fish and cook, turning once, until browned, 6 minutes total. Drain on paper towels.
Combine the greens, tomatoes, pecans and onion. In a jar with a lid, shake the honey mustard and remaining 5 tablespoons olive oil; pour over the salad and toss. Serve the fish on top of the salad.