Preheat oven to 425°. Line a large rimmed baking pan with foil; spray with nonstick spray.

Toss fennel, 1 Tbsp. olive oil, ¼ tsp. salt and ¼ tsp. pepper in a medium bowl until coated. Spread evenly in half of the prepared baking pan. Place strawberries, cut sides down, in other half of pan.

Roast fennel and strawberries for 8 to 10 minutes or until tender and lightly browned (do not stir). Cool slightly.

Meanwhile, combine lemon zest and juice, vinegar, honey, vanilla and remaining ¼ tsp. salt and ¼ tsp. pepper in a small bowl. Gradually whisk in remaining ¼ cup olive oil until combined.

Combine mixed greens, roasted fennel and strawberries and honeydew in a large serving bowl. Drizzle with 2 Tbsp. dressing; gently toss to coat.

Garnish with fennel fronds and pistachios, if desired. Serve with remaining dressing.