Preheat your oven to 425°F. Prepare a baking sheet by lightly drizzling it with a little olive oil or lining it with parchment paper.
Trim and cut the broccoli into florets, then toss with a small drizzle of olive oil, salt, and pepper. Spread the broccoli evenly on the baking sheet.
Roast the broccoli in the oven for about 15-18 minutes or until edges are slightly crisp and charred.
While the broccoli roasts, prepare the cauliflower by cutting it into florets. Boil or steam the cauliflower until tender, about 8-10 minutes.
In a small pan over medium heat, lightly toast two garlic cloves (or add them raw into the mash if you prefer a stronger flavor) for extra depth, then peel and mince them.
Drain the cauliflower and transfer it into a bowl. Add the minced garlic, 1 tsp olive oil, a pinch of salt, and pepper; mash until smooth with a fork or potato masher. Adjust seasoning as needed.
Season the salmon fillet with salt and pepper on both sides. Heat a non-stick skillet over medium-high heat.
Sear the salmon fillet for about 3-4 minutes per side until a golden crust forms and the salmon is cooked through but still moist in the center.
Plate the salmon alongside a serving of roasted broccoli and a generous scoop of garlic mashed cauliflower. Serve immediately while hot.