In this plant-based version of an ahi tuna dish, sugars from the watermelon form a glaze that comingles with pepper as the steak sears in the pan. A very hot griddle surface, lightly greased, will ensure an even sear that stays intact. The steaks don’t need much time to sear. If you prefer a firmer steak, cook for less time. A longer sear will result in a softer steak with more sweetness from the caramelization.