Add your oil to a deep pot over medium heat, along with your chorizo, yellow onion, celery, and garlic. Cook until the chorizo is browned & the vegetables are fragrant (about 5-7 minutes).
Add in your whole cherry tomatoes & fresh thyme, and cook for another 2-3 minutes.
Add in your water, vegetable bouillon, lentils, & salt / pepper to taste. Bring to a boil, reduce to a simmer- then cover & cook for 20-30 minutes until the lentils are cooked through and the cherry tomatoes have popped. You can pop the tomatoes with the back of a wooden spoon if they don’t on their own.
About 5 minutes before serving, add in your chopped chard leaves & stems, and stir to combine. Leave uncovered & cook for roughly five minutes.
Ladle the soup into a bowl, and top with thinly sliced red onion.