Prepare your ingredients by dicing the onion, slicing the bell pepper, and mincing the garlic and ginger.

Heat a large pan over medium heat and add a splash of oil. Sauté the diced onion until it becomes translucent.

Add the minced garlic and grated ginger to the pan and sauté for an additional minute until fragrant.

Stir in the red curry paste and mix well, continuing to cook for about a minute.

Pour in the coconut milk and stir to combine, allowing the mixture to come to a gentle simmer.

Gently add the salmon fillets and sliced bell pepper, ensuring they are submerged in the sauce.

Add the lime juice and fish sauce. Stir in the fresh spinach, allowing it to wilt into the sauce.

Cook for 10-12 minutes until the salmon flakes easily with a fork and the spinach has wilted.

Taste and adjust seasoning if necessary, adding more fish sauce or lime juice according to preference.

Serve the curry hot, garnished with fresh cilantro, over a bed of steamed rice or alongside crusty bread.