Simmer 1/2 cup sugar and 1/2 cup lemon juice over medium heat. Let it simmer for a few minutes until the sugar dissolves and thickens slightly. Set aside.
In a small bowl, combine heavy cream, 2 Tablespoons lemon juice, and vanilla. In another bowl, whisk together flour, baking powder, baking soda, and salt.
Cream together the butter and 1 cup sugar. Add eggs one at a time.
Beat in the the flour in 3 additions.
Alternate with cream mixture.
Fold in the blueberries.
Add batter to a large loaf pan (or 9 2 1/2 by 4 baking pans) that has been coated with cooking spray.
Bake in a preheated 350 degree oven for 30 minutes, or until a toothpick comes out clean. Brush the top of the cake with lemon syrup. Let stand for 15 minutes, then turn the tea cake out. Brush the remaining syrup all over the cake. Cool completely.