Place a large frying or griddle pan on a high heat. Slice the lemon in half. When the pan is smoking hot, add the lemon flat-side down and sear for 2-3 mins till charred. Remove the lemon from the plan and place on a clean plate. Allow to cool for 5 mins. Keep the pan on the heat.

Meanwhile, snap the ends from the asparagus (they will naturally break off at the woody part when you gently bend the spears). Pop the asparagus in a bowl and drizzle over 2 tsp olive oil. Toss to mix. Carefully lay the asparagus spears in the pan with a pinch of salt and cook for 2-4 mins, turning them regularly till lightly charred on all sides. Take the pan off the heat.

When the lemon has cooled, squeeze the juice into a small bowl. Peel and grate in the garlic clove. Scoop in the wholegrain mustard. Drizzle in 1 tbsp olive oil. Season with salt and pepper. Whisk well to make a smooth dressing.

Arrange the asparagus onto a serving plate. Drizzle over the dressing. Season with some cracked black pepper and serve.