Peel the onions and finely chop them. Scrub and trim the carrots, then slice them on the angle into 1cm-thick pieces. Trim and cut the courgettes into small pieces. Peel and thinly slice the garlic. Fill and boil your kettle.
Pour 2 tbsp olive oil into a large pan and warm to a medium heat. Add the veg and garlic, along with a good pinch of salt and pepper. Fry for 10 mins, stirring occasionally, till the veg begin to soften.
Add the lentils to the pan and crumble in the stock cube. Pour in 1.25 ltrs boiling water and bring to the boil, then reduce to a gentle simmer. Cover with a lid (you can use a baking tray if you don’t have a lid that fits) and cook for 25 mins, till the lentils and carrots are tender.
Meanwhile, strip the kale leaves off their woody cores and roughly shred the leaves. When the lentils are cooked, stir in the kale and bubble for 2-3 mins to wilt it.
Take the pan off the heat. Grate in the lemon zest and squeeze in a little juice. Stir in the pesto. Taste the stew, and add more salt, pepper or lemon juice if needed, then ladle into warm bowls and serve.