Preheat oven to 400°F (200°C). Cut pita into 1-inch pieces. Toss pita pieces with 2 tbs olive oil, 1 tsp salt, and 1 tsp black pepper until evenly coated. Spread in a single layer on a baking sheet and bake 8–12 minutes, tossing once, until crisp and golden. Remove and let cool; they will firm up as they cool.

Dressing

Make dressing

In a small bowl or jar combine 4 tbs extra-virgin olive oil, 3 tbs fresh lemon juice, 1 tbs red wine vinegar, 1 minced garlic clove, 1/2 tsp Dijon mustard, 3/4 tsp salt, and 1/2 tsp black pepper. Whisk vigorously or shake in a jar until emulsified and smooth. Taste and adjust seasoning (add more lemon for brightness or more salt to taste).

Salad

Prepare vegetables and herbs

Wash and dry romaine leaves thoroughly, then chop or tear into roughly 1–2 inch pieces to yield about 3 cups. Peel (if desired) and dice cucumber into 1/2-inch pieces to make ~1 cup. Seed (if very juicy) and dice the tomato to make ~1 cup. Thinly slice radishes and green onion. Roughly chop parsley and julienne the mint.

Assemble salad

Place romaine, cucumber, tomato, radish slices, parsley, mint, and green onion into a large mixing bowl. Drizzle about two-thirds of the dressing over the salad (reserve the rest to adjust final seasoning). Toss gently but thoroughly so the dressing coats vegetables evenly.

Add pita croutons and finish

Add the toasted pita pieces to the dressed salad and toss once to combine—this keeps them slightly crisp. Taste and add remaining dressing as needed. Sprinkle 1 tsp sumac over the top if using, and additional salt or pepper to taste. Serve immediately so pita remains crunchy.