Spoon your tahini into a large bowl. Peel and finely chop or grate your garlic. Swirl it through the tahini along with the zest from your lemon, 1 tbsp lemon juice, 1 tsp cumin and a pinch of salt. Taste. Add more cumin or lemon, a little pepper, more tahini and/or a splash of water, till it's so good you want to eat the lot.
Drain and rinse your lentils. Fold them through the tahini dressing.
Peel your carrot. Use your veg peeler to turn your peeled carrot into ribbons but basically continuing to 'peel' it till you get to the centre (or get bored). Nibble the rest of the carrot or thinly slice and add it to the salad, along with the ribbons.
Mound the watercress on top. Halve, peel and thinly slice your onion. Get a frying pan hot. Add 1 tbsp oil. Swirl the onion through the oil. Add a pinch of salt. Sizzle over medium-high heat till golden and crisp. Spoon over the salad.
Thinly slice your chilli. Sizzle it in the remaining oil (add more, if needed) till a little crisp. Scatter over the salad. Finish with a final gloss of oil, spritz of lemon juice and a dusting of cumin.