Baked Artichoke and Spinach Dip

Ingredients (16)

• 2 (10-ounce) bags fresh baby spinach, rinsed, stems removed
• 4 tablespoons unsalted butter (1/2 stick), plus more for the dish
• 1 cup chopped yellow onion
• 1 tablespoon minced garlic
• 1 teaspoon kosher salt
• 1/2 teaspoon freshly ground black pepper
• 1/4 teaspoon cayenne
• 1/4 cup all-purpose flour
• 1 cup milk
• 1 cup heavy cream
• 2 teaspoons fresh lemon juice
• 1 cup cubed rindless brie cheese
• 1 cup shredded Monterey Jack cheese
• 1 (6.5-ounce) jar marinated artichoke hearts, drained and coarsely chopped
• 4 strips bacon, fried crisp, drained, and chopped
• 1/4 cup grated Parmesan