Place the cauliflower on a baking tray lined with baking paper, drizzle with oil, season with salt. Top with the Sbrinz cheese. Bake the cauliflower in the centre of an oven preheated to 220 °C for approx. 15 mins.
Mix the lemon juice, oil and pesto in a large bowl. Without adding any oil, toast the walnuts in a non-stick frying pan until golden brown.
Combine the walnuts, lettuce and dressing, season with salt, serve with the cauliflower.