I do not marinate them.
When cleaning remove the outer membrane (the dark coloured one).
Cut into larger size pieces (or whole).
Ligtly brush with oil.
Put on medium heat.
After 1 minute turn over,
Than sprinkle mix of salt, chili powder and ground cumin on the top side.
After 1 minute turn again sprinkle as above.
Turn over every minute.
Total cooking time maybe 5-6 minutes depending on heat.
Much better on charcoal BBQ, and mesh (not plate)