A little butter. But also using a properly seasoned cast iron skillet. It will still stick a little bit but then I use a little metal “brownie spatula” from Pampered Chef which is perfect for scraping things like this.
1 X Pampered Chef Mini-Serving Spatula #2622 (perfect for cutting and serving brownies) https://www.amazon.com/dp/B07NP7YMB5/ref=cm_sw_r_cp_api_glt_fabc_F93CDRB3VE9RR2KT9D9P?_encoding=UTF8&psc=1