1For the cake:
Preheat oven to 325 degrees. Grease a 10 inch tube pan with 2 tablespoons butter. Sprinkle pan with 1/4 cup sugar. Mix together 2 3/4 cups flour, baking powder and salt. Set aside. In a large bowl, cream together 1 cup butter and 2 cups sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla. Gradually beat in the flour mixture. Dredge blueberries with remaining 1/4 cup flour, then fold into batter Pour batter into prepared pan.
Bake in the preheated oven for 70 to 80 minutes, or until a toothpick inserted into the center of the cake comes out clean. Let cool in pan for 10 minutes, then turn out onto a wire rack and cool completely. Slice to serve and top with Lemon Curd.
2For the sauce:
Remove the zest (rind) from the limes using a zester or a peeler (be careful to avoid getting any of the white pith). Juice the lemons after removing the zest.
In a medium saucepan over medium-high heat, combine lemon zest, lemon juice, and sugar. Bring just to a boil; reduce heat to medium-low and simmer 5 minutes. Add butter and stir until it has melted. Remove from heat and cool to room temperature.
NOTE: Use a heavy-based, non-reactive saucepan. Stainless steel, anodized aluminum, and enamel all work well. Aluminum or unlined copper pans will react with the acid in the lemons, discoloring the curd and giving it a metallic flavor. Beat eggs into cooled lemon mixture until well blended. Return to heat and cook over medium-low heat, stirring constantly, 10 to 15 minutes or until
mixture thickens and coats spoon.
NOTE: Do not let the lemon curd boil, as it can cause the mixture to curdle. Remove from heat. The lemon curd will continue to thicken as it cools. Makes approximately 2 cups.
* Cold lemons are much easier to grate. Always grate your lemons first, and then juice them. Grate lemons just before using as the zest will lose moisture if it sits too long.
** Do not use the bottled lemon juice - only use fresh-squeezed lemon juice.
Room temperature lemons produce more juice. When choosing lemons, look for ones that are firm, plump, and heavy for their size. Always use fresh lemons when making lemon curd.
*** Use good quality butter. Do not use butter substitutes.