Season the salmon fillet lightly with salt and pepper. Let it sit at room temperature while you prep the vegetables.
For the cauliflower mash, steam the cauliflower florets in a steaming basket over boiling water for about 8-10 minutes until tender.
Meanwhile, lightly toss the asparagus in 1 tsp olive oil, salt, and pepper. Steam them in a separate steaming basket or add during the final 4 minutes of the cauliflower steaming process.
In a small saucepan, gently heat the remaining 2 tsp olive oil with a crushed garlic clove to infuse the flavor, then remove the garlic.
Once the cauliflower is soft, transfer it to a bowl and mash until smooth, drizzling in a little of the garlic-infused olive oil. Season with additional salt and pepper if needed.
Heat a non-stick skillet over medium-high heat. Sear the salmon skin-side down for about 3-4 minutes until the skin is crisp, then flip and cook for an additional 3-4 minutes, or until the salmon reaches your desired doneness.
Plate the salmon alongside the steamed asparagus and top the cauliflower mash with a drizzle of the remaining garlic oil. Finish with a squeeze of fresh lemon juice over the salmon and vegetables before serving.