Preheat your oven to 400°F (200°C). Toss the cubed butternut squash with olive oil, salt, and pepper. Spread in a single layer on a baking sheet and roast for 25-30 minutes, turning halfway, until tender and lightly caramelized. Remove and let cool slightly.
While the squash roasts, place the pumpkin seeds in a dry skillet over medium heat. Toast for 3-5 minutes, shaking occasionally, until fragrant and golden. Set aside to cool.
Prepare the lemon vinaigrette by combining lemon juice, olive oil, Dijon mustard, honey or maple syrup, minced garlic, salt, and pepper in a small bowl or jar. Whisk or shake vigorously until well emulsified.
In a large bowl, gently toss the mixed greens with about two-thirds of the lemon vinaigrette until evenly coated.
Add the roasted butternut squash, diced apples, and red onion (if using) to the dressed greens. Toss gently to combine.
Sprinkle the crumbled goat cheese, toasted pumpkin seeds, and dried cranberries over the top of the salad.
Drizzle the remaining vinaigrette over the completed salad and serve immediately for the best flavor and texture.
