On a large rimmed baking sheet add the butternut squash cubes, 3 tbsp olive oil, 1 tbsp salt, 2 tsp black pepper, and 1 tbsp chili powder. Toss to coat the squash.
Bake for 30-40 minutes, or until the squash is easily pierced with a fork. Remove and allow to cool for 5 minutes.
Cook Lentils
Meanwhile, in a medium saucepan add the chicken stock and bring to a boil. Add the lentils and turn down to medium-low. Simmer 15-20 minutes, until the lentils are tender but not mushy. Remove from the heat and allow to cool for a few minutes. Drain off any excess stock.
Balsamic Vinaigrette
In a small bowl or mason jar add the vinaigrette ingredients (1/4 cup olive oil, 1 tbsp balsamic vinegar, minced garlic, 1 tsp dijon mustard, 1 tsp sriracha sauce, kosher salt, and black pepper) screw on the lid and shake vigorously to combine. (or whisk if using a bowl).
Assemble Salad
In a large serving bowl add the roasted red pepper, crumbled feta, baby spinach leaves, choppedparsley, chopped pistachios, squash, drained lentils, and vinaigrette. Toss lightly to combine. Taste for seasoning then serve immediately.