
Preheat oven to 325 degrees F (162 degrees C)
Heat a small saucepan over medium heat. Add the balsamic vinegar. When it reaches a low boil, reduce the heat to medium-low and continue cooking for 15-20 minutes, or until reduced by half. Set aside.
While the dressing is heating up, prepare the onions by combining the red wine vinegar, water, sugar, and salt in a small bowl or mason jar. Whisk or shake to combine. Add the onion, cover, and place in the refrigerator to infuse/pickle for 15 minutes.
Place the slivered almonds on a rimmed baking sheet and bake for 7-10 minutes, or until slightly golden brown. Set aside.
Add the reduced balsamic vinegar and remaining dressing ingredients to the bowl of a food processor or blender (I used my vitamix). Blend to combine. Taste and adjust the seasonings as needed.
Place the spinach, strawberries, pickled onions and hemp seeds (optional) in a large bowl. Top with the almonds and desired amount of dressing. Toss to coat and serve immediately.
Leftovers keep (separately) in the refrigerator for 2-3 days, though best when fresh.