Heat a large pot over medium heat and add the olive oil, allowing it to shimmer.
Add the chopped onion and minced garlic to the pot, sautéing until fragrant and translucent, about 5 minutes. The onions should turn golden and smell sweet.
Stir in the diced carrots and celery, cooking for another 7 minutes until the vegetables soften slightly and release their aroma.
Add the ground turmeric to the vegetables, stirring for about 30 seconds until the spice becomes fragrant and the mixture turns a warm golden hue.
Pour in the vegetable broth and bring the mixture to a gentle simmer, watching for bubbles to form around the edges.
Add the rinsed red lentils to the pot, stirring to combine, then cover and let simmer uncovered for 20-25 minutes until the lentils are tender and have absorbed the flavors.
Stir in the chopped tomatoes and coconut milk, simmering for an additional 5 minutes to meld the flavors and create a velvety, golden broth.
Taste the soup and season with salt and pepper as desired, adjusting the flavors until balanced and vibrant.
If you prefer a creamier texture, use an immersion blender to blend part of the soup directly in the pot, then stir to combine, creating a smooth, velvety consistency.
Remove the soup from heat and let it sit for 5 minutes to settle and develop richer flavors.
Serve hot, garnished with fresh herbs or a squeeze of lemon for brightness, and enjoy this comforting, colorful bowl.