Heat oil in a skillet and sauté red curry paste until fragrant and deep in color.
Add protein of choice and cook briefly until coated and lightly browned.
Pour in coconut milk, broth, soy or fish sauce, and sugar, then stir until smooth and simmering.
Add bell peppers, carrots, and zucchini, and let the curry simmer until the vegetables are tender and flavors meld.
Stir in spinach to wilt, squeeze in fresh lime juice, and adjust seasoning to taste.
Serve hot over jasmine rice and garnish with cilantro or basil.