Place 6 quarts of water in a large pot, add barley and 1 tbsp salt. Cover, bring to a boil, reduce and cook for 25 to 45 minutes (follow instructions on barley package as cooking times can vary per brand).
While barley cooks, grate the zest of the lemon over a large bowl.
Add the juice of the lemon
Add 1/2 tsp salt, 1/4 tsp pepper, and 3 tbsp olive oil. Whisk gently.
Add 1/4 cup chopped red onion and set aside.
Line a baking sheet with parchment paper.
Once barley is cooked, drain it thoroughly and spread it into the baking sheet to let it cool down.
Slice scallions, chop parsley, cilantro or any other herb you want to use.
Slice carrots very thin.
Add cooled barley to the dressing in the bowl, stir gently.
Add scallions, herbs and carrots, a pinch of salt and pepper and mix throughly.
Serve cold or at room temperature.