Sauté the aromatics: Heat the olive oil in a large, heavy-based pot over a medium heat until it shimmers and smells fragrant. Add the diced onion and cook, stirring occasionally, for about 5 minutes until the pieces turn translucent and begin to soften. You should hear a gentle sizzle, and the kitchen will fill with a sweet, savoury aroma.

Add the vegetables and chicken: Tip in the garlic, carrots, celery, and red bell pepper. Stir everything together and cook for another 5 minutes. The vegetables will start to release their moisture, and the mix will look glossy and smell deeply earthy. Add the cubed chicken breast and cook until the outside turns opaque and slightly golden, about 4 minutes, stirring frequently so it doesn't stick.

Bloom the spices: Sprinkle the cumin, smoked paprika, dried thyme, black pepper, and salt over the chicken and vegetables. Stir continuously for about 1 minute. The spices will become intensely aromatic, and you'll see the colour deepen as they coat everything in a warm, reddish tint. This step is crucial for unlocking the full flavour.

Add the lentils and liquids: Pour in the rinsed red lentils, followed by the chicken stock and the can of chopped tomatoes. Stir everything well, scraping the bottom of the pot to lift any browned bits. The liquid will look slightly murky at first, but that's perfectly normal.

Simmer until tender: Bring the soup to a gentle boil — you'll see bubbles breaking the surface steadily — then reduce the heat to low, cover, and let it simmer. After about 25 minutes, check the lentils. They should be soft and beginning to fall apart. The soup will have thickened noticeably, and the colour will be a rich, golden-orange. If it seems too thick for your liking, add a splash more stock or water.

Finish with lemon: Remove the pot from the heat and stir in the lemon juice. This brightens the entire soup, cutting through the richness and making the flavours sing. Taste and adjust the salt if needed. The soup should be creamy, with tender pieces of chicken and a velvety texture from the broken-down lentils.

Rest and serve: Let the soup sit for 5 minutes before ladling it into bowls. This allows the flavours to settle. Garnish with fresh parsley if you like, and serve hot. The steam will carry a comforting, spiced aroma that signals a nourishing meal ahead.