Mix the Creole seasonings with pecan halves and pulse in a food processor several times until the nuts only have a few large pieces left, then scatter the mix out on a large plate.
Lay the clean and dry fish fillet down on top of the seasonings and press lightly to get the nuts to stick. Be sure to lay the pretty side (or what the industry calls the "presentation side") down in the nuts. They will end up facing up on the finished plate.
In a medium-hot pan, drizzle a little olive oil in, then gently place the fish fillet inside, pecan side down. Gently shake the pan back and forth just a little to keep the fish from sticking to the bottom of the pan. Nonstick pans work exceptionally well for cooking fish.
Cook on the first side for approximately 1½ to 2 minutes, being careful not to let the nuts burn. If the pecans turn black and smoke, the dish must be started over using a cooler pan.
Turn the fillet over gently, then continue cooking until the fish is done. If the fish is very thick, place the entire pan in a 375° oven (as long as it's an oven-safe pan) and finish cooking in the oven after flipping.
Remove fillet from the pan and let rest on a warm plate while you make the sauce. Add shrimp, shallots, and garlic to the same fish pan, turn up the heat to high,and sauté lightly, then add white wine.
Allow the wine to reduce by a little more than half, then add the tomatoes, cilantro, and butter.
Swirl the entire contents continually until the butter melts, season lightly with salt and pepper, squeeze in the lime juice, then pour over the fish fillet and serve immediately.