Put pine nuts into a dry pan and toast over high heat until they are just starting to color and become fragrant, watching very carefully so they don't burn, 2-4 minutes
Mix together the lemon juice and balsamic vinegar; then whisk in 3 T of extra-virgin olive oil, one tablespoon at a time. Taste the dressing to see if you want to add a little more oil and if so, whisk it in. Season the dressing with sea salt and freshly ground black pepper. Grate the parmesan cheese, using medium or large side of the grater.
Wash baby arugula if needed and spin dry or dry with paper towels. (It usually comes pre-washed in a 5 oz. container.)
Put arugula in a large bowl and toss with just enough dressing to coat all the leaves. (You may not need all the dressing.) Add the coarsely grated Parmesan and toss a few times to combine, then add about 3/4 of the toasted pine nuts (or almonds) and toss again. Put salad into individual serving dishes and top each one with a few more toasted nuts.