Pat the fish fillet dry with paper towels (1 minute). Season both sides generously with salt and pepper (1 minute). Halve the cherry tomatoes, finely chop the garlic and parsley (3 minutes). Measure out capers and olives (1 minute).

Heat the olive oil in a large skillet over medium-high heat (1 minute). Add the fish fillet and sear for 4-6 minutes per side, depending on thickness, until golden brown and cooked through (12 minutes total cooking time). Remove fish from skillet and set aside.

Add the halved cherry tomatoes and chopped garlic to the same skillet. Cook, stirring, until tomatoes start to soften and release their juices (4 minutes). Add the capers and olives and cook for another minute (1 minute). Stir in the chopped parsley.

While the sauce simmers, prepare the polenta: Bring the water to a boil in a small saucepan (2 minutes). Slowly whisk in the quick-cooking polenta. Reduce heat to low and cook, stirring constantly, for 5-7 minutes, until thickened (7 minutes total cooking time). Stir in the butter and a pinch of salt.

Return the fish to the skillet with the sauce for 1 minute to heat through (1 minute).