Preheat the oven to 350°F (190°C).
Cut the Napa cabbage in half through the core then cut each half into quarters. You will have 8 Napa cabbage wedges. Set aside.
In a small bowl combine the tomato paste, garlic, coriander, cumin, turmeric, and black pepper. Stir to combine completely. Set aside.
Heat 1/4 cup (60 ml) of the olive oil in a large cast-iron skillet over medium-high heat. Working in batches, if necessary, add as many cabbage wedges into the skillet cut side down as will comfortably fit. Season with the coarse kosher salt. Cook, turning once, until lightly charred, about 2-3 minutes per side. Transfer the seared cabbage to a plate and repeat with any remaining cabbage quarters.
Carefully, wipe out the skillet and reduce the heat to medium. Add the remaining 1/4 cup (60 ml) olive oil to the skillet, once warm and beginning to shimmer add the spiced tomato paste mixture. Heat, stirring constantly, until the tomato paste begins to split and darken in color, 2-3 minutes.
Add enough water to the skillet to come halfway up the sides, about 1 - 1 1/2 cups (240-350 ml) total. Season the liquid with salt and bring to a simmer.
Nestle all of the seared cabbage wedges into the simmering tomato broth, overlapping if necessary. Transfer the cabbage to the oven and bake, uncovered, turning the cabbage wedges once about half way through, about 40-50 minutes. The cabbage should be falling apart tender when cooked completley.
Serve immediatley garnished with cilantro leaves and pistachio crumble if using.