Heat the olive oil in a large pot over medium heat. Add the diced onion and cook for 3 minutes until it softens.
Stir in the garlic and ginger. Cook for 1 minute until fragrant.
Add the cumin, turmeric, and garam masala. Stir for 30 seconds to toast the spices.
Pour in the diced tomatoes with their juices and the vegetable broth. Add the rinsed red lentils, salt, and black pepper. Bring the mixture to a boil, then reduce to a simmer. Cook for 10 minutes, stirring occasionally, until the lentils are tender.
Gently add the salmon pieces to the pot. Simmer for 5 to 7 minutes until the salmon is cooked through and flakes easily.
Remove the pot from the heat. Stir in the chopped cilantro. Serve with lime wedges on the side.