Line a mini loaf pan (3x5 inch) with plastic wrap. If you don't have a mini loaf pan you can use a small bowl, custard cups or even muffin tins.
Measure out soy milk, then stir in 1 teaspoon of apple cider vinegar and 1/8 teaspoon salt. Allow mixture to stand for about 10 minutes so that it curdles and thickens.
Put the melted coconut oil and the canola oil in the bowl of a food processor or blender, then add the soy milk, lecithin and turmeric (if using). Process for about 2 minutes or until smooth.
Carefully pour mixture into the mini loaf pan, then transfer to the freezer for 1 hour to set.
You should get about 1 cup of vegan butter. To use it in baking, weigh out 114 grams for every half cup.