Creating the Juicy Blueberry Upside Down Cake is a joyous experience when you follow these simple steps:

1. Preheat the Oven: Begin by preheating your oven to 350°F (175°C). Grease a 9-inch round cake pan or use a springform pan for easy removal.

2. Prepare the Blueberries: In a small saucepan over medium heat, combine the blueberries with ½ cup of the granulated sugar. Stir gently until the berries start to soften, which should take about 3-5 minutes. Set aside to cool.

3. Make the Butter Mixture: In a separate mixing bowl, melt the butter. Add the remaining ½ cup of sugar and mix until well combined.

4. Add Eggs and Vanilla: Beat in the eggs one at a time, followed by the vanilla extract, blending until the mixture is smooth.

5. Combine Dry Ingredients: In another bowl, mix together the flour, baking powder, and salt. Gradually add this dry mixture to the wet mixture, alternating with the milk. Blend until just combined; avoid over-mixing.

6. Layer Blueberries in the Pan: Pour the cooked blueberries (along with any juices) evenly into the bottom of the prepared cake pan.

7. Add Cake Batter: Gently pour the cake batter over the blueberries, being careful not to disturb the berry layer below.

8. Bake the Cake: Place the cake in the preheated oven and bake for 40-45 minutes, or until a toothpick comes out clean when inserted into the center.

9. Cool the Cake: Once baked, remove the cake from the oven and let it cool in the pan for about 15-20 minutes. This step is vital for ensuring that the cake holds its shape.

10. Invert the Cake: Carefully run a knife around the edges before inverting the cake onto a plate. The blueberries should now be beautifully arranged on top.

11. Serve Warm or Room Temperature: Let the cake cool fully before slicing, or serve it warm with a dollop of whipped cream or a scoop of vanilla ice cream.

Following these straightforward steps will lead you to a deliciously rewarding Juicy Blueberry Upside Down Cake that is sure to be a hit.