In a large bowl, stir together self-rising flour, cornmeal, sugar, and baking powder.
In another bowl whisk together buttermilk and eggs until blended, then pour into dry mixture. Let batter rest while you make the sauce.
In a small saucepan set over medium heat, combine blueberries, sugar, jalapeño, and lemon juice and stir well.
Cook for about 5 minutes, mashing the blueberries with your spoon or a potato masher to release juices, leaving some blueberries whole if you like. Let simmer gently while you cook the pancakes.
To make the pancakes, warm a skillet or griddle over medium heat. When warm, add a small amount of butter to the pan and swirl to coat.
Stir the 4 tablespoons melted butter into the batter. Scoop 1/4 cup of batter and drop it into the prepared pan, repeating as allowed for pan size.
Cook until edges are dry and bubbles appear (2-3 minutes), then flip and cook an additional 2-3 minutes, until golden. Remove to a plate and repeat until all batter is used, adding butter to the pan between each batch.
Serve with warm blueberry jalapeño sauce. Leftover sauce can be stored in the fridge and reheated as needed.