In a large mixing bowl, combine flour, sugar, and cold butter. Use a pastry cutter or your fingers to mix until the mixture resembles coarse crumbs, approximately 5 minutes. Press this crumbly mixture evenly into the bottom and sides of a tart pan. Place the crust in the refrigerator to chill for at least 30 minutes.

Preheat your oven to 350°F (175°C). Once the crust has chilled, remove it from the refrigerator and poke small holes in the bottom using a fork to prevent bubbling. Bake the crust in the preheated oven for about 15-20 minutes, or until it turns lightly golden and feels firm to the touch. Let it cool in the pan while you prepare the filling.

In a medium saucepan, whisk together eggs, fresh lemon juice, lemon zest, and sugar until smooth and well combined. Place the saucepan over low heat, stirring continuously for 5-7 minutes. Be cautious not to let it boil, as you want the filling to thicken without scrambling. Once slightly thickened, remove from heat and let cool for a few minutes.

Carefully pour the lemon filling into your baked crust, spreading it evenly. Return the tart to the oven and bake for an additional 20-25 minutes, or until the filling is just set around the edges but slightly wobbly in the center. A slight jiggle is perfect, as it will continue to firm up while cooling.

After baking, remove the Kentucky Derby Lemon Tart from the oven and allow it to cool at room temperature for about 30 minutes. Once cooled, cover the tart with plastic wrap and refrigerate for at least 2 hours, or until fully set. This chilling step enhances the flavors and ensures a perfect slice.

Once set, carefully dust the top of the tart with powdered sugar for an elegant finish. For added freshness and color, top with a sprinkle of fresh berries if desired. Slice into beautiful wedges and serve your delightful Kentucky Derby Lemon Tart at your next gathering, ready to impress everyone!