Place the vinegar, onion and dates in a small bowl, add a pinch of salt and mix well with your hands. Allow it to sit for 20 minutes, then drain any residual vinegar and discard.
Meanwhile, heat the butter and 1 tbsp olive oil, in a medium sized frying pan over medium heat. Add the pita and cook for 5-6 minutes, stirring constantly until the pita is crunchy and golden brown. Remove from the heat and stir in the sumac, chile flakes and ¼ teaspoon of salt. Allow to cool.
Once ready to serve, toss the spinach leaves and pita mix in a large bowl. Add the dates and red onion, the remaining olive oil, lemon juice, and another pinch of salt. Serve immediately.
Recipe by Cooks and Kid at https://cooksandkid.com/baby-spinach-salad/