In a medium bowl, cream together the shortening and sugar until light and fluffy. This step helps give the cake its soft texture.

Beat in the egg until thoroughly combined. You'll start to see the mixture take on a creamy consistency.

In a separate bowl, sift together the flour, salt, and baking powder. This step ensures the cake has an even rise and a fine crumb.

Add the dry ingredients to the creamed mixture a little at a time, alternating with the milk. Mix gently until everything is combined—don't overmix.

Carefully fold in the blueberries. Try to use fresh berries if possible, and gently incorporate them to avoid squishing.

Grease an 8-inch square baking pan and pour the batter into it. Smooth the top with a spatula.

In a small bowl, combine sugar, flour, cinnamon, and softened butter. Cream thoroughly until it forms a soft, crumbly texture.

Generously cover the top of the cake batter with the crumb mixture. It might seem like a lot, but trust me, you want every bit of that cinnamon-sugar goodness.

Let the cake cool slightly before slicing. Enjoy warm or at room temperature. It's even better the next day!