Start by slicing the carrots and finely chopping the red onion. Arrange the carrots on one side of a baking tray and place the grapes on the other, scattering the chopped onion over the grapes. Drizzle both with olive oil, season with salt, and use your hands to gently coat everything—try to keep the carrots and grapes separated so they roast evenly.

Meanwhile, prepare the dressing by adding all the ingredients to a small jar and shaking well until smooth.

To assemble the salad, combine the drained lentils, roasted carrots and grapes, crumbled feta, chopped almonds, and fresh mint in a large bowl. Pour over the dressing, toss gently to coat, and serve.