Preheat your oven to 400°F and line a baking sheet with parchment paper.
Trim the woody ends off the asparagus and toss with half of the olive oil, sea salt, and black pepper.
Spread the asparagus on the baking sheet and roast for 10-12 minutes until tender-crisp.
While the asparagus roasts, steam the cauliflower florets and garlic clove until very soft, about 8-10 minutes.
Drain the cauliflower well and process in a blender or food processor until smooth and creamy, seasoning with salt to taste.
Pat the cod fillet dry with paper towels and season both sides with salt, pepper, and a pinch of paprika if desired.
Heat the remaining olive oil in a non-stick skillet over medium-high heat.
Sear the cod for 3-4 minutes on the first side until a golden crust forms, then flip and cook for another 2-3 minutes until opaque.
Spoon the cauliflower mash onto a plate, top with the seared cod, and serve with the roasted asparagus and a fresh lemon wedge.