Halve, peel and chop the shallot into small ½cm pieces. Halve, peel and slice the red onion into thin half-moons. Cut the cherry tomatoes in half. Peel and grate the garlic (or use a garlic press). Remove the mint leaves from their stalks. Discard the stalks and chop the leaves. Slice each halloumi block into eight slices. Drain the lentils in a sieve or colander and rinse under cold water.
Drizzle a good glug of olive oil into a saucepan on medium heat and add the red onion. Cook until really soft, 7 mins. Add the balsamic vinegar, pop a lid on and turn the heat down to low. Cook until nicely caramelised, stirring occasionally, 8-10 mins. Transfer to a bowl and set aside. Wipe out the pan.
Heat a drizzle of oil in another frying pan on medium heat, add the shallot. Cook until soft, 5 mins. Add the tomatoes, a pinch of salt and black pepper. Cook for 5 mins more. Add the garlic and stir. Cook for another minute. Next add the lentils along with another pinch of salt and black pepper. Stir together. Warm through for 3 mins. Add the baby spinach, pop a lid on and leave to the side (off the heat) to wilt the spinach
While the spinach wilts, put the (now empty) pan you used for the onions on medium heat and add a drizzle of oil. Once the oil is hot, lay in the halloumi slices. Cook for 3 mins on each side until golden. Remove the pan from the heat.
Add half the mint to the lentil mixture and stir together (if the spinach hasn't wilted completely, that's fine!).
Serve the lentil mixture in bowls with the halloumi slices on top. Spoon over the caramelised red onion and finish with the remaining mint and pumpkin seeds.