Combine the shredded beets, carrots, and apple in a mixing bowl, and toss to combine.
In a small bowl, whisk together the lemon juice and salt until the salt is dissolved. Drizzle in the olive oil and add a few grinds of black pepper, and whisk until blended. Pour the dressing over the shredded vegetables and toss until evenly dressed. Taste, and add more salt and pepper if needed. Serve immediately, or allow to sit for up to 1 hour.