Using your sharpest filet knife with a very fine blade and tip, carefully slice through the center of the fish’s belly from the tail to the head, so the fish butterflies open. If just pulled from the water, scrape the entrails, rinse the fish and carefully lift out the bones. If just pulled from the local fishmonger’s case, the heavy lifting will have already been done for you.
Line the bottom of a cast-iron skillet or heavy-bottomed pan with a generous slick of olive oil. Get the pan good and hot before adding the capers (but be careful as the capers will splatter!). Fry the capers until browned and just before crunchiness, 6–7 minutes. Add 3 tablespoons of the butter and allow it to melt before adding the lemon. Finally, add the wine. Take care here, as the wine will flare up in the pan (to avoid this, shut the burner, move the skillet to a neighboring burner and add the wine before returning the skillet to the medium-high heat). Continue to simmer until the mélange is reduced to a thickened sauce. Set the pan on the back burner, as your work here is done.
Next, preheat oven to 400°. Grease your largest cast-iron skillet or heavy baking dish with a thick swipe of the remaining 1 tablespoon of butter. Mix together the almond and white flours with a bit of salt and a couple of generous grinds of pepper. Very lightly coat the opened, butterflied fish on both sides with the flour mixture and lay the fish, flesh side down, in the greased vessel. Find your longest spatula. You’ll need it to turn the butterflied fish over after 3–4 minutes. Once flipped, cook for another 3 minutes. Remove the fish from the oven and using your long spatula (or the famous spatula/spoon combo), remove the fish to a platter.
Spoon the caper sauce onto the trout and serve accompanied by halved lemons and an old Chardonnay from California or France.