Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
In a small mixing bowl, combine the almond flour, finely chopped fresh basil, lemon zest, and half of the sea salt and black pepper.
Trim the woody ends off the asparagus and place the spears on one side of the prepared baking sheet.
Toss the asparagus with 2 teaspoons of the olive oil, the minced garlic, and the remaining salt and pepper, spreading them out into a single layer.
Pat the halibut fillet completely dry with a paper towel, then brush the top with the remaining teaspoon of olive oil.
Press the basil-almond mixture firmly onto the top of the halibut to create an even crust, then place the fish on the other side of the baking sheet.
Roast for 12 to 15 minutes, depending on the thickness of the fillet, until the fish is opaque and flakes easily with a fork.
Remove from the oven and immediately drizzle the fresh lemon juice over both the halibut and the roasted asparagus before serving.