Add the lemon juice, honey, Dijon mustard, olive oil, salt, and pepper to a small bowl or mason jar. Whisk everything together really well until the honey dissolves into the dressing. The dressing will look creamy and slightly emulsified. You can make this step up to 24 hours ahead and just shake it again before using.
Wash your fresh strawberries under cool running water and pat them completely dry with a clean kitchen towel. Slice them into thin, even pieces—I aim for about 1/4 inch thick so they don't get mushy when tossed with the dressing. Set them aside while you prep the other vegetables.
Rinse your baby spinach and pat it dry really well (wet spinach will make your dressing all watered down). If you're using regular spinach leaves, tear them into smaller, bite-sized pieces. Put the spinach in your serving bowl—this is where the magic starts to come together.
Thinly slice your red onion into half-moons and dice the cucumber into small chunks. The red onion adds a peppery bite that balances all the sweetness from the strawberries and honey. Don't skip the cucumber either—it adds freshness and keeps things from feeling too heavy.
If you haven't already toasted your pecans, pop them in a dry skillet over medium heat for about 3 minutes, shaking the pan occasionally. The second you smell that nutty aroma, they're done—don't walk away because they'll burn super fast. Transfer them to a plate immediately so they stop cooking.
Toss the spinach with about half of your dressing first, just enough to coat the leaves lightly. Add the sliced strawberries, diced cucumber, red onion, and most of the toasted pecans. Gently toss again to combine everything without breaking up the berries or bruising the greens.
Divide the spring strawberry salad recipe into four bowls or plates and drizzle with any remaining dressing. Top with the reserved pecans and crumbled feta cheese right before serving. Taste it and add a tiny pinch more salt if you need it—every person's palate is different.