Preheat oven to 400 degrees F. Grease a 9-inch pan (square or round).
Melt the butter in either a microwave-safe dish or in a small saucepan; remove from heat if applicable.
Stir in the sugars, salt and cinnamon; combine well.
Add the flour and stir to combine well. It's best to work this with your fingers after the flour is stirred in as the crumbs seem to form better. Set aside.
In a large bowl, combine the flour, sugar, baking powder and salt. Stir well.
In a smaller bowl, whisk together the milk, melted butter and the egg.
Stir the milk mixture into the flour mixture until just combined. Don't overmix!
Pour into prepared pan. Drop teaspoonfuls of raspberry jam randomly over the top of the batter. Swirl gently with a spoon--just for a slight marbling effect. Don't combine the jam and the batter.
Top with crumbs. Bake at 400 degrees F for 25 minutes or until toothpick inserted in center comes out clean (of cake batter).
Cool completely on rack. Dust with confectioners' sugar if desired.