Rinse the cabbage remove the visible bad leaves, and cut it into 6 wedges.: The leaves should feel crisp and cool when you rinse them, and cutting into wedges exposes the layered structure so heat penetrates evenly. Use a sharp knife to slice through the core, you will hear a clean, decisive sound as the blade passes through. If the outer leaves are wilted or torn, remove them first to keep the wedges tidy. A common mistake here is leaving the core too intact, which can make wedges fall apart while cooking, so trim the base slightly to help wedges hold their shape.
Add about 1/2 to 1 inch of lightly salted water to a large deep skillet or Dutch oven, and bring to a boil.: You want the water level low enough that it will steam the wedges rather than fully submerge them, producing a gentle, enveloping heat that softens without turning the leaves mushy. As the water heats, you will notice faint steam and a rising shimmer on the surface. If the water is too high, the cabbage will sit soggy, so aim for that shallow depth. Avoid using a wide shallow pan where water evaporates too quickly, because uneven cooking can result.
Add the cabbage wedges and 1/2 teaspoon of salt. Cover and simmer over medium heat for 8 to 10 minutes.: Once the pan is covered, the aroma will shift to a vegetal sweetness, and small beads of condensation will gather on the lid. This steam is what cooks the cabbage through. After about eight minutes, a fork should slide into the thickest part with gentle resistance. If the fork goes in too easily, the cabbage may be overcooked and mushy, which you want to avoid. A common error is cooking at too high heat, which makes the outer leaves collapse before the center softens.
Turn cabbage on the other side, work gently, and simmer for an additional 8 to 10 minutes or until tender.: When you flip the wedges, do it carefully so they keep their shape, and listen for a soft sizzle as they settle back into the pan. The interior will become translucent and the layers will separate slightly, signaling tenderness. Continue checking with a fork; the goal is tender but not falling apart. Too vigorous turning can bruise the leaves, so be gentle and patient.
Discard the water and return the pan to the stove over low heat, until the moisture has evaporated entirely.: As the excess water evaporates, the pan will go quiet and you will see a faint film left on the surface. This step concentrates flavor and prevents diluted seasoning, leaving the cabbage ready to accept the melted butter . Watch closely because once dry, the bottom can brown quickly. A pitfall here is leaving too much water which will prevent the butter from coating properly.
Add the melted butter and gently toss the cabbage to coat.: When you pour in the warm butter , there should be an audible soft hiss and an immediate glossy sheen on the leaves. Use tongs or a spatula to turn the wedges, making sure the butter seeps into the layered pockets. This finish smooths out the texture and adds richness. If you add cold butter , it will seize and fail to distribute evenly, so always melt it first.
Sprinkle with salt and pepper, red pepper flakes, and a squeeze of lemon juice. Serve with lemon wedges and garnished with parsley.: The final seasoning brightens and balances the dish, with the tang of lemon cutting through the richness of the butter and the warmth of the black pepper and red pepper flakes adding depth. You will notice a fresh citrus perfume as you squeeze the wedges. Taste before serving to adjust salt and pepper. Over seasoning at this point is a common misstep because concentrated flavors can become overpowering, so add cautiously and taste.