In a small bowl, whisk vinegar, olive oil, poppy seeds, honey, mustard, salt, and pepper for the dressing.
Place the spinach in a large bowl and add strawberries and onion.
Add feta and pecans.
Put dressing on the salad as you eat it to avoid spinach from getting soggy.
Notes
Make it a meal: Add chicken or steak.
No Feta: Leave off or use goat cheese
Leftovers: Store dressing in refrigerator and top salad per serving to preserve spinach
