If you want to get ahead, you can soak the cashews in a bowl of cold water overnight. This isn't essential, but it does make a slightly creamier dressing.
Heat your oven to 200C/Fan 180C/Gas 6. Put a large roasting tin on the top shelf of your oven to heat up.
Peel the carrots. Halve or quarter them lengthwise, depending on how big they are. Cut the pepper into 2cm thick strips, discarding seeds and stem. Halve, peel and cut the onion into 2cm slices. Toss everything in a bowl with 2 tsp olive oil. Season well with salt and pepper.
Tumble the veg into the hot roasting tin. Shake the tin to even everything out in one layer. Roast on the top shelf for 30 mins or till everything is golden around the edges.
If you've soaked your cashews overnight, drain them. If not, pop the cashews in a pan with just enough water to cover. Simmer for 5 mins. Drain.
Tip the cashews into a food processor or blender. Add 1/2 tsp turmeric with a pinch of salt. Finely grate in the zest from the lemon. Squeeze in the juice from one half. Add 2 tbsp water and the dates, squeezing out the stone. Blend to a smooth paste. The dressing should be thick and smooth, so if it is too thick trickle in a little cold water till it seems right to you. Taste the dressing and add more salt, pepper or another squeeze of lemon juice if you think it needs it.
Once the veg is cooked, drain the lentils and rinse well. Peel and chop the garlic. Add them and a pinch or two of chilli flakes to the roasting tin. Pop back in the oven for 5 mins to warm through.
Roughly chop the herbs, leaves and stalks. Fold them through the warm lentil and roast veg salad. Serve with spoonfuls of the dressing.