Preheat your oven to 350°F (175°C). Spread the raw pecans in a single layer on a baking sheet. Toast them for about 8-10 minutes until fragrant and lightly browned. Keep an eye on them to prevent burning. Let cool and chop roughly.

In a medium bowl or jar, combine balsamic vinegar, olive oil, poppy seeds, honey, Dijon mustard, kosher salt, and ground black pepper. Whisk or shake until emulsified and smooth. Set aside.

In a large serving bowl, combine spinach, strawberries, and red onion. Drizzle half of the dressing over the salad and gently toss to coat.

Crumble feta cheese and add it along with the toasted pecans. Gently toss again and serve immediately with remaining dressing on the side.