In a medium saucepan, combine 2 cups of fresh blueberries with sugar over medium heat. Mix 1 tablespoon of cornstarch with 2 tablespoons of water and stir this slurry into the pot. Cook the mixture for about 5 minutes, or until it thickens and bubbles gently, then fold in the remaining blueberries. Once thickened, remove it from the heat and let it cool to room temperature.

Zest two lemons to capture their vibrant flavor and then juice them to yield approximately ½ cup of juice. In a small pot, whisk together 4 egg yolks and ½ cup of sugar until smooth. Stir in the lemon juice and cook on medium heat, stirring continuously, until the mixture thickens—this should take about 8-10 minutes. Remove from heat, then whisk in 6 tablespoons of cold butter and the lemon zest until completely melted. Chill the curd in the refrigerator for at least 30 minutes.

Preheat your oven to 375°F (190°C) if using a homemade tart shell. Bake the tart shell until it turns golden brown, about 15-20 minutes, then let it cool completely. Once cooled, fill the tart shell with the chilled lemon curd, spreading it evenly. Gently layer the cooled blueberry compote over the curd without blending it in.

After assembling the Blueberry Lemon Curd Tart, cover it with plastic wrap and refrigerate for at least 1 hour before serving. This allows the flavors to meld and the tart to set beautifully. When ready to serve, slice into wedges and enjoy the delightful combination of creamy lemon curd and sweet blueberry compote!