Prepare the Ingredients: Wash the spinach and raspberries. Slice the avocado and toast the walnuts in a dry skillet over medium heat until fragrant.

Make the Dressing: In a small bowl, whisk together olive oil, balsamic vinegar, salt, and pepper.

Assemble the Salad: In a large bowl, combine spinach, raspberries, avocado slices, and toasted walnuts. Drizzle the dressing over the salad and gently toss to combine.

Serve: Divide the salad onto plates and sprinkle with crumbled feta cheese if desired. Enjoy immediately!