After sear-roasting salmon pour off any excess fat from the skillet. Using a large wad of paper towels, blot any remaining oil from the pan, but leave any browned bits. Return pan to high heat and add wine, shallots and rosemary. Cook, stirring, until wine is almost completely evaporated, 3-4 minutes. Remove from heat and whisk in cubes of butter, adding a few at a time until they're all thoroughly incorporated and the sauce is thick and creamy looking. (If the butter is slow to melt, set the pan over low heat). Stir in lemon juice, season with salt and pepper to taste, and serve immediately, spooned over sear-roasted salmon.