Heat oven to 400°F. Toss asparagus and cherry tomatoes with olive oil, half the garlic, ¼ tsp salt, and a pinch of pepper. Divide vegetables among four 12-inch foil squares, piling in the center.

Pat salmon dry and place one fillet on top of each pile. Dot with butter, then sprinkle remaining garlic, ¼ tsp salt, and 2 tsp dill over the fish. Add a couple of lemon slices to each packet.

Fold foil over salmon, crimp edges to seal, and place packets on a baking sheet. Bake 15 to 18 minutes, until salmon flakes easily.

Let packets rest 1 minute, then carefully open. Squeeze reserved lemon juice over the fish and top with fresh dill. Serve warm in the foil.