If you're not nut-free, you can use any nut butter you like here (like peanut butter or almond butter). For the nut-free folks, I found that the sunflower seed butter had a milder, less noticeable flavor than the tahini, but sunflower seed butter also has the tendency to turn baked goods green! It doesn't affect taste, just appearances, but something to keep in mind. The cookies pictured are made with tahini - I didn't find the flavor to be too noticeable, but it does add a bit of nuttiness! That being said, taste your tahini before using to make sure you enjoy the flavor. Certain brands of tahini can be more bitter, and that flavor will translate, so make sure you like the tahini plain before adding it to your cookies!
If you don't want/need to use flax eggs, replace the two flax eggs with 1 egg + 1 egg yolk.