Heat your oven to 200°C/Fan 180°C/Gas 6. Put a roasting tin in the oven to heat up.
Halve the tomatoes horizontally. Peel and finely chop the garlic. Put half the garlic in a bowl with 1 tsp olive oil, ½ tsp ground cumin and a pinch of salt and pepper. Mix well. Arrange the tomatoes in the preheated tin, cut side up. Roast for 30 mins.
While the tomatoes roast, whisk the remaining garlic and cumin with 1 tbsp olive oil and 1 tbsp red wine vinegar to make a dressing. Set aside.
Strip the mint leaves from their woody stems (you can use the stems to make mint tea - they’re just as flavourful as the leaves). Finely chop the mint leaves and all of the parsley, leaves and stalks.
Drain and rinse the lentils. Once the tomatoes have roasted for 30 mins, add the lentils, the dressing and the chopped herbs to the warm tin. Gently mix everything together (mixing everything in the roasting tin means you’ll be mopping up all the tomato juices in the tin). Scoop the salad onto warm plates. Crumble the feta over the top and tuck in.