Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
In a large bowl, toss the cauliflower florets with half of the olive oil, half of the garlic powder, half of the smoked paprika, and half of the salt and pepper.
Spread the cauliflower in a single layer on the prepared baking sheet and roast for 22 minutes until the florets are tender and the edges are golden-brown.
While the cauliflower roasts, pat the salmon fillet dry with a paper towel and season both sides with the remaining garlic powder, smoked paprika, salt, and pepper.
Heat the remaining olive oil in a medium non-stick skillet over medium-high heat until the oil is shimmering.
Place the salmon in the skillet and sear for 4 minutes without moving it to develop a crispy crust, then flip and cook for 3 more minutes until the center is just opaque.
Arrange the roasted cauliflower on a plate, top with the pan-seared salmon, and finish with a fresh squeeze of lemon juice.