How ould you adjust the recipe - using Black Sesame Seed Butter?

This will be easiest if you're working with a scale. According to Kind Arthur Baking, 1/4 cup of sesame seeds weighs 35g, so skip the grinding step and add 35g of the sesame butter in step 4. If you don't have a scale, then according to the link you shared, 2T of sesame seed butter is 33g, so use about two tablespoons.