Preheat your oven to 400°F (200°C). Spread the diced beets on a lined baking sheet, drizzle with olive oil, and season with salt and pepper. Roast for about 25–30 minutes until tender and slightly caramelized.
Rinse the buckwheat under cold water first. Bring water or broth to a boil, add buckwheat, then reduce heat and simmer for 10–15 minutes until tender but not mushy. Let it sit covered for a few minutes before fluffing.
Dice the apple into small cubes just before assembling to keep it fresh. Toast the walnuts in a dry skillet over medium heat for 3–5 minutes until fragrant, then let them cool.
In a small bowl, whisk together olive oil, apple cider vinegar, maple syrup (or honey), Dijon mustard, salt, and pepper. Mix until smooth and slightly thickened.
In a large bowl, combine cooked buckwheat, roasted beets, diced apples, toasted walnuts, and dried cranberries. Pour the dressing over the mixture and gently toss until everything is evenly coated. Finish with fresh parsley.
Allow the salad to rest for 10–15 minutes so the flavors blend together. It can be served at room temperature or lightly chilled.