1. Preheat oven to 350 degrees Fahrenheit
2. Place salmon in a sheet pan lined with aluminum foil
3. Season the salmon with olive oil, salt, and pepper
4. Bake for 16 minutes (salmon will be a tad underbaked)
5. Remove from the oven and flake into large chunks with a fork
6. Meanwhile steam asparagus for 2-3 minutes

For Bechamel

1. Warm the milk in the microwave
2. In a saucepan, melt the butter over medium-low heat
3. When the butter is melted, add the flour and whisk until everything is incorporated and the flour is cooked (about 45 seconds to 1 minute)
4. Add the warm milk and whisk vigorously to avoid lumps
5. Keep whisking until the sauce starts getting thick and creamy
6. Add the dill
7. When the sauce boils, remove from heat and add the dijon mustard, lemon juice, gruyere cheese, salt, and pepper. Mix until combined and check for seasoning

Assembly

1. Place 3 sheets of lasagna noodles on the bottom of a rectangular 9x13" baking dish
2. Add 1/3 of the sauce and place the steamed asparagus in a single layer
3. Top with 1/2 cup of mozzarella cheese, salt, and pepper
4. Top with 3 more lasagna noodles
5. Add 1/3 of the sauce
6. Place all the salmon making sure it covers the whole layer
7. Top with 1/2 cup of mozzarella cheese
8. Top with 3 more lasagna noodles
9. Add the rest of the sauce and spread to cover the whole surface
10. Add 1 cup of mozzarella cheese and gruyere
11. Bake for 30 minutes
12. Broil for 2-3 minutes or until the top has browned
13. Remove from the oven and let it sit for 15 minutes before cutting
14. Enjoy!