In that case, try boiling a mixture of baking soda and water in it, then scouring it using tongs with copper wool (I’d probably use steel wool, but that might also leave scratches, I don’t know). If it’s giving your food a taste, it is coming off, just really gradually and under high heat.
Are those scorch marks an issue beyond aesthetics though? (Genuinely curious, not judging)
They leave a burnt taste in the food
In that case, try boiling a mixture of baking soda and water in it, then scouring it using tongs with copper wool (I’d probably use steel wool, but that might also leave scratches, I don’t know). If it’s giving your food a taste, it is coming off, just really gradually and under high heat.