Method
- Roast the beets — Preheat oven to 200°C (400°F). Toss the beetroots with olive oil and a pinch of salt. Wrap in foil and roast until a knife slides in easily, about 50 minutes.
- Peel and slice beets — Once cool enough to handle, peel the beets (skins should rub off easily) and slice into rounds or wedges. Set aside.
- Cook the lentils — Rinse the lentils and place in a pot with plenty of water and the bay leaf. Bring to a boil, then simmer until tender but still holding their shape, about 25 minutes.
- Drain and season lentils — Drain the lentils well, remove the bay leaf, and season lightly. Keep warm.
- Season the steak — Pat the steak dry and season all over with salt and pepper. Heat the butter in a heavy pan over high heat until foaming.
- Sear the steak — Sear the steak on all sides until well browned, basting with the butter as it cooks. Reduce heat and cook to your liking (about 3–4 minutes per side for medium-rare). Rest for at least 5 minutes before slicing.
- Make the dressing — Whisk together the wholegrain mustard, Dijon mustard, red wine vinegar, olive oil, and honey until emulsified. Season to taste.
- Assemble and serve — Spread the warm lentils over a large platter. Slice the rested steak and arrange over the lentils along with the roasted beets. Drizzle generously with the mustard dressing, scatter over the parsley, and serve immediately.
