Preheat your oven to 425°F for the asparagus and prepare a baking sheet by drizzling half the olive oil over it.
Toss the asparagus with a pinch of salt, pepper, and half the garlic powder if desired, then arrange in a single layer on the baking sheet.
Roast the asparagus in the preheated oven for about 10-12 minutes until tender and lightly charred.
Meanwhile, steam the cauliflower florets until they are very tender, about 8-10 minutes.
Transfer the steamed cauliflower to a bowl and mash it with a fork or immersion blender. Stir in a splash of lemon juice, remaining olive oil, salt, and pepper to taste for a creamy consistency.
Season the cod fillet with the remaining garlic powder, salt, and pepper. Heat a non-stick skillet over medium-high heat.
Once the skillet is hot, add the cod fillet and sear for about 3 minutes per side until the fish is opaque and flakes easily.
Plate the seared cod alongside a serving of roasted asparagus and a generous scoop of cauliflower mash. Drizzle additional lemon juice over the cod if desired, and serve immediately.