Dice potatoes. Heat 2 tbsps olive oil in non stick pan, add garlic cloves and sauté till light brown.
Sprinkle some salt on a plate. Add cumin powder and crushed peppercorns and mix well. Coat the fish pieces with this mixture.
Add all capsicum pieces to pan and toss. Add salt and toss again. Sauté for 2-3 minutes. Cut 2 lemons into thick slices. Transfer sautéed vegetables into a bowl.
Add 1 tbsp oil to the same pan. Place 4 lemon slices in two groups on the pan and place one fish piece on each of them and cook for 2 minutes.
Place potatoes in a bowl. Chop jalapenos and add and mix well. Squeeze juice of ½ lemon and add. Flip fish pieces alongwith lemon slices and cook till both sides are equally done.
Transfer vegetables onto a serving dish. Sprinkle salt on top and drizzle 1½ tsps olive oil. Place cooked fish pieces on top alongwith lemon slices. Serve immediately.