Place the eggs in a blender and blend on medium-high speed until frothy and fluffy, about 45 seconds. Add flour, milk, lemon zest, sugar, salt, and vanilla, and blend until combined. The batter is thin. Set aside and allow to rest for 15 minutes at room temperature, or cover and refrigerate it for up to 24 hours. (No need to bring to room temperature before baking.)

Preheat the oven to 400°F (204°C). Place butter in a 10-inch oven-safe skillet (or any 3-quart baking dish), and place in the oven for just 5 minutes to melt the butter. (Be sure not to leave it in the oven to burn!) Remove from the oven and use a pastry brush to spread the melted butter up the sides of the pan.

Pour the batter into the center of the hot pan. No need to swirl it around. Place it in the oven and bake for 15 minutes. Keeping the Dutch baby pancake in the oven, reduce the temperature to 350°F (177°C) and bake for 10 more minutes, or until the edges and center are browned.

Remove from the oven and cool for 5 minutes before adding desired toppings. Slice and serve.

The pancake is best enjoyed right away, but you can cover and store leftovers in the refrigerator for up to 5 days, or in the freezer for up to 2 months.