In a large cast iron skillet, heat 1 tablespoon of coconut oil over medium heat. Saute bell peppers, snow peas, and baby corn for 4-5 minutes, until vegetable soften. The veggies should still have a crunch/snap to them, but should be mostly cooked through. Set aside.
Add remaining tablespoon of coconut oil to pan and saute onion until translucent. Add red thai curry paste and tomato paste, then use a spatula to stir until paste dissolves. Add spices and cook for 1-2 minutes, until fragrant. Reduce heat to a simmer. Add coconut milk, making sure to stir the coconut milk before pouring into the skillet as the fat and liquid tend to separate. Stir to combine. The curry should have a deep yellow color. Taste and add sugar, salt and pepper to taste. Cook for 1 minute.
Return the cooked vegetables to the skillet, stirring to coat them in the curry. Simmer uncovered for 5 minutes to allow curry to deepen in flavor. If the curry starts to dry out, add some water or broth.
To serve, squeeze 1 lime wedge onto the curry and top with fresh basil. Serve over rice.