In a small bowl, whisk together balsamic vinegar, olive oil, dijon mustard, honey, salt, and pepper.

In a skillet over medium heat, melt the butter, then add the chopped pecans and brown sugar. Cook for about 5 minutes until the pecans are toasted and fragrant.

In a large bowl, combine the baby spinach, sliced strawberries, crumbled feta cheese, and thinly sliced red onion.

Pour the dressing over the salad and toss gently. Top with toasted pecans before serving.