In a large skillet or Dutch oven, heat 1 tablespoon of oil over medium heat. Add the onion and cook until softened and lightly browned, about 5 minutes.
Stir in the Thai red curry paste, garlic, and ginger. Cook, stirring constantly, for 1 minute until fragrant.
Pour in the coconut milk and water, stirring to combine everything. Bring the sauce to a gentle simmer and let it cook for 10 minutes for the flavors to develop.
Meanwhile, heat the remaining 1 tablespoon of oil in a nonstick skillet over medium-high heat. Place the halloumi slices in a single layer and cook for 1 to 2 minutes per side, until golden brown and crisp. Set aside.
To the simmering curry, add the sugar snap peas, bell pepper, tamari, and brown sugar. Cook for about 3 minutes, until the vegetables are tender-crisp.
Remove the curry from the heat. Stir in the fresh lime juice and chopped cilantro.
Taste the curry and adjust seasoning if needed, adding more curry paste for heat or sugar for sweetness.
Divide cooked rice and curry among four bowls. Top each bowl with the seared halloumi slices before serving.