Remove the pith and seeds from the peppers and dice them.

Dice the tomatoes, onion, and cucumber.

Toss the diced vegetables together in a wooden or ceramic bowl.

In a separate small bowl, stir together the salt, pepper, lemon juice, and minced garlic.

Slowly whisk in the olive oil into the lemon juice mixture.

Pour the dressing over the vegetables, mix well.

Sprinkle with sumac or za'atar, if desired.

Serve immediately or chill for later.