Heat coconut oil in a large Dutch oven or heavy-bottomed pot over medium heat. Once shimmering, add diced onion and sauté for 3 minutes until softened and fragrant. The onion foundation builds flavor for everything that follows.
Stir in minced garlic and fresh ginger, cooking for exactly 1 minute until the raw bite disappears. Add curry powder and cumin, stirring constantly for 30 seconds to bloom these spices and release their essential oils.
Add diced zucchini, yellow squash, red bell pepper, and green beans to the pot with bloomed spices. Stir everything together and cook for 2 minutes to begin releasing vegetable juices into the aromatic base.
Pour in coconut milk, diced tomatoes (with their liquid), and vegetable broth, stirring to combine thoroughly. Bring the summer veggie curry crowd dinner to a gentle simmer and cook uncovered for 18-20 minutes until vegetables are tender but still slightly firm.
Taste and adjust seasoning with salt and black pepper as needed—remember that it will concentrate slightly as it sits. Stir in fresh cilantro and squeeze lime juice throughout, which brightens the meatless summer sauce significantly.