Preheat the oven to 350°F. Arrange the pecans in a single layer on an ungreased baking sheet. Toast for 8 to 10 minutes, stirring occasionally, until they release a nutty aroma and the interior turns a warm tan color when broken in half. Keep a close watch during the final minutes to prevent burning. Transfer the toasted pecans to a cutting board and roughly chop them once cooled.

Place the thinly sliced red onion in a bowl of cold water and let them soak while preparing the rest of the salad. This step helps mellow the sharp bite of raw onion while preserving its crisp texture.

In a small mixing bowl or a large liquid measuring cup, whisk together the balsamic vinegar, extra-virgin olive oil, poppy seeds, honey, Dijon mustard, salt, and black pepper until fully emulsified. Alternatively, combine the ingredients in a mason jar, seal it tightly, and shake vigorously until well blended.

In a large serving bowl, arrange the baby spinach as the base. Scatter the quartered strawberries evenly over the greens. Drain the red onion and add it to the mix. Drizzle half of the dressing over the salad and gently toss to coat the leaves. Assess the amount of dressing— the spinach should be lightly coated but not drenched. Adjust with more dressing if needed. Finally, sprinkle in the crumbled feta and chopped pecans, giving the salad a light toss just before serving.

Serve immediately with additional dressing on the side for those who prefer extra flavor.