Step 1: In a small bowl or measuring cup, combine the cold soy milk and apple cider vinegar. Stir once and set aside for 5 minutes. The milk will curdle slightly and thicken into a vegan buttermilk. This is exactly what you want.

Step 2: Melt the coconut oil gently in the microwave or on the stovetop. It should be liquid but not hot. Let it cool to about room temperature. If it is too hot, it will prevent the butter from emulsifying properly.

Step 3: Pour the melted coconut oil, sunflower oil, curdled soy milk mixture, salt, lecithin, and turmeric (if using) into a high-speed blender. Blend on high for 60 to 90 seconds until the mixture is completely smooth, frothy, and uniform.

Step 4: Pour the mixture into a glass container, silicone butter mold, or a parchment-lined loaf pan. Tap the container gently to remove air bubbles.

Step 5: Place in the freezer for 15 to 20 minutes to kick-start setting, then transfer to the refrigerator for at least 4 hours or until completely firm. The butter will solidify as the coconut oil cools.