Cook the wine and shallot in a saucepan over medium-high heat. When the wine has almost evaporated and the sauce has formed a glazy texture (about 7 minutes). Remove the pan from the heat and whisk in the butter a couple of cubes at a time until melted and the sauce is thick and creamy; briefly return the pan to low heat if the butter is slow to melt. Off the heat, stir in the dill, lemon zest, lemon juice, red pepper flakes, 1/2 tsp. salt, and several grinds of pepper. Season to taste with more lemon juice, salt, and pepper.
Preheat the oven to 425 degrees. Toss asparagus in oil, sea salt and crushed peppercorn. On a baking sheet lined with parchment paper, place lemon slices on ½ the sheet. Fill the other half with the asparagus. Brush salmon fillets with olive oil, season with lemon juice, salt, pepper, and dill. Bake for 13-15 minutes or until cooked to your preference.
Plate salmon, and asparagus. Drizzle a hearty spoonful of the lemon-dill Beurre Blanc sauce over the salmon. Zest half a lemon over the asparagus, and add a pinch of sea salt and garnish with the roasted lemon slices. Serve immediately.