Mix semolina and salt. Add warm water gradually and knead for 8 to 10 minutes until firm and smooth. Cover and rest for 30 minutes.
Roll the dough very thin with a pasta roller or rolling pin. Dust with semolina, cut into fine noodle strands, and let dry for 15 minutes.
Cook the Sauce:
Heat olive oil in a Dutch oven. Soften the onion for 5 minutes, then add chicken, cinnamon, pepper, and 1 teaspoon salt.
Add stock, bring to a gentle simmer, and cook covered for 30 minutes. Add chickpeas and turnips and simmer for 15 minutes, then add zucchini and cook 12 minutes more until tender.
Steam and Serve:
Steam the noodles over simmering water or broth for 15 minutes. Transfer to a wide bowl, loosen with a splash of water and half the butter, then steam once more for 10 to 15 minutes.
Toss the hot noodles with remaining butter and salt. Arrange on a platter with chicken and vegetables and moisten with several ladles of white sauce.
Notes
Keep the sauce pale by avoiding tomato and heavy browning.
If using purchased fresh rechta, follow its steaming time and begin with the sauce.