Trim leaves and woody stalk from the cauliflower, then cut through the root into 8 wedges. Season both sides of each wedge with salt and pepper. Reserve any loose cauliflower pieces.
In a large skillet or Dutch oven, heat the oil over medium-high heat. Place one layer of the wedges in the skillet cut-side down and cook without moving them until well browned on one side, 3 to 4 minutes. Transfer to a plate and continue until all the cauliflower is seared, adding more oil as needed. Return all the cauliflower to the pan with uncooked side facing down.
Add 1/4 cup water, any loose cauliflower pieces, 2 teaspoons black pepper, rice-wine vinegar, soy sauce, sugar, garlic, bay leaves and Thai chile. Cover and let simmer over medium heat until the cauliflower is crisp-tender, about 5 minutes.
Uncover, turn the heat to medium-high, and cook, basting the cauliflower occasionally with the sauce, until the cauliflower is tender and the sauce has thickened and reduced to about 3/4 cup, 8 to 10 minutes.
Serve the cauliflower with plenty of sauce and a sprinkle of scallions.
Tip If you plan to eat rice with the adobo, bring 1 3/4 cups water to a boil in a medium saucepan before you start the recipe. Stir in 1 teaspoon salt and 1 cup long-grain rice, cover, and let simmer on the lowest heat possible for 18 minutes. Proceed with the adobo. Let the rice sit, covered and off the heat, until the adobo is ready. Fluff rice with a fork before serving.