1. Preheat the oven to 220 degrees Celsius.
2. Cut the cauliflower into florets. Place the cauliflower in an oven-proof dish or baking sheet with the salmon fillets. Pour over the rapeseed oil and season with pepper, then bake in the oven for 20 minutes.
3. Drain and rinse the lentils thoroughly then toss into the finely chopped spinach and drizzle with the olive oil and lemon juice.
4. Serve the lentil salad topped with the baked cauliflower and salmon fillet.