Heat the oven to 200 C / 400 F with a rack in the middle. Pat the salmon dry with paper towels. Zest one lemon, juice it, and set both aside for the mash. Cut the second lemon into 8 thin rounds. Drain and rinse the beans.

Spread the asparagus on one half of a 33 x 46 cm / 13 x 18-inch rimmed sheet pan and toss with 1 tbsp olive oil and 1/4 tsp salt. Set the salmon skin-side down on the other half. Rub with the remaining 1 tbsp oil, 1/4 tsp salt, pepper, and paprika, then top each fillet with 2 lemon rounds. If a fillet has a thin tail, fold the last 3 cm under so it cooks at the same pace as the thick end.

Bake for 12 to 15 minutes, until the thickest part of the salmon reads 145 F / 63 C and the flesh is opaque and flakes with a fork. The asparagus should be tender with browned tips.

While the pan bakes, heat 2 tbsp olive oil in a 3-quart / 2.8 L saucepan over medium heat for 1 minute. Add the garlic and thyme and cook for 45 to 60 seconds until fragrant but not brown. Add the beans, 60 ml water, and 1/2 tsp salt, then simmer for 5 minutes until the beans are soft and most of the water is absorbed.

Take the saucepan off the heat and mash the beans with a potato masher until mostly smooth with a few whole beans left. Stir in the lemon zest, 2 tbsp of the lemon juice, and 1/4 tsp pepper. Add a splash of water if the mash feels stiff, then cover to keep warm.

Divide the mash among 4 plates, top with a salmon fillet, and set the asparagus alongside. Squeeze the roasted lemon rounds over the fish and serve right away.