Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.

Wrap the beetroots in aluminum foil, drizzle with olive oil, sprinkle with salt, and place on the baking sheet alongside the salmon.

In a pot, combine green lentils with water; bring to a boil and simmer for about 20-25 minutes until tender, then drain.

In a bowl, whisk together Dijon mustard, lemon juice, olive oil, salt, and pepper.

Place the salmon fillets on the baking sheet; brush generously with the mustard mixture and sprinkle herbs on top.

Bake everything for 15-20 minutes until the salmon is flaky and cooked through.