Freeze cabbage overnight (or for up to 3 days). Thaw at room temperature for at least 4 hours. Then, cut out core and separate leaves. Alternatively, blanch cabbage: Bring a large pot of water to a boil. Using a sharp paring knife, cut out the core. Using tongs, gently lower the cabbage into the pot and cook until the outer leaves are tender, about 2 to 4 minutes. Carefully remove the outer leaves to a towel-lined tray with tongs, and continue with remaining cabbage until you have about 12 to 15 leaves. Using a paring knife, shave off thick stem at the base of each leaf.
Make the sauce: In a medium saucepan over medium heat, melt the butter. Add the onion and season with ¼ teaspoon salt. Cook, stirring occasionally, until tender, about 5 to 6 minutes. Add garlic and sauté until fragrant, about 1 minute. Transfer half of cooked onion mixture to a large bowl. Then, add tomato sauce, diced tomatoes, vinegar, tomato paste, honey, and paprika to saucepan. Bring to a boil, then reduce heat and simmer for 15 minutes to allow flavors to meld. Taste and season with salt and pepper as desired.
Roll cauliflower rice in a clean kitchen towel to absorb excess moisture. Add turkey to bowl with reserved onion mixture along with cauliflower rice, ½ cup sauce, 1¼ teaspoons salt, and ½ teaspoon pepper. Mix until well combined.
Preheat oven to 350 degrees F. Spread 1½ cups sauce on the bottom of a 9-by-13-inch baking dish. Thoroughly pat cabbage leaves dry. On a cutting board, place a cabbage leaf with the stem facing you. Place ¼ cup filling in the middle, near the base, and spread into a cylinder. Firmly roll the base of the leaf over the filling, tucking in the sides, until it forms a small packet. Place the cabbage roll seam side-down in the baking dish. Repeat with remaining leaves and filling; you should have about 12 leaves. Spoon remaining sauce over the rolls.
Cover the dish with foil and bake until the filling is cooked through and the dish is bubbling, about 70 to 90 minutes. Serve hot.