Sticky black residue on cast iron skillet

We made homemade soft tacos (wheat) and used the cast iron. There’s some sticky residue that doesn’t come off when washed with soap. I boiled water in the skillet few times but it’s still sticky.

We made homemade soft tacos (wheat) and used the cast iron. There’s some sticky residue that doesn’t come off when washed with soap. I boiled water in the skillet few times but it’s still sticky. We only used oil on it when we made the tacos. How can it be washed? submitted by /u/Bubbly_Ad6528 [link] [comments]