I am going to give you my version of fish yassa and I hope you like it. This one I used flounder and any type of fish can be used in this recipe.
I cut these fish in to 3 pieces because the fillet is so large I had no other choice but to cut it this way. It is also a very soft fish and it would scatter right away so this is step one to keeping this delicate piece of fish intatact.
Step two is that made a marinade by adding to the bowl, 2 pinches of mustard powder, 1 tbs of lemon juice, 1 pinch of pink salt, 1 pinch of black pepper corns that I ground with mortar and pestle, 1 bullion cube crushed, 2 dashes of maggi or knorr aroma and 1 pinch of red chili powder stir and combine add the fish and half of an onion sliced in half moon pieces and let it sit for 10 minutes in the fridge.
Step three and the final step is adding 1 cooking spoon full of olive oil to the cast iron skillet and cut the remaining half of the onion in to half moon pieces then fry them until they are translucent. Take one clove of garlic and grind it in the mortar and pestle and added it to the sauteed onions and take the fish out of the fridge that is marinating and add this and the entire marinade to the skillet. Do not throw it away because it is part of the sauce and cook the fish until it is opaque. Add 5 olives and the 1tbs of the brine from the olives in to the fish and turn off the stove.
Eat this with rice.

