Preheat the oven to 300ºF.
Beat the softened butter & cream cheese on low speed until creamy and fluffy. Gradually add the sugar, beating 5-7 minutes or until sugar is incorporated and soft peaks form. Add eggs one at a time and blend just until the yolk disappears. Add vanilla and mix well to incorporate.
Combine flour and salt and gradually add to butter mixture, continually beating at low speed until blended after each addition. Once blended, beat batter on a low or medium-low speed for a few minutes until it looks fluffy with soft peaks.
Pour batter into greased silicone cupcake pan. Do not fill each well more than half to three-quarters full or they’ll spill over during the baking process and you’ll have to trim them.
Place the silicone cupcake pan on a baking sheet for stability. With an ovenproof 2-cup measuring cup (such as Pyrex glass), fill the measuring cup with 2 cups water and place in the oven with the cupcake pan.
Bake at 300ºF at 45 minutes to one hour (the time will depend on your oven) or until a toothpick inserted in the center comes out clean.
Once the pound cakes are mostly cooled but still warm, remove from the silicone mold and place upside down on a baking sheet lined with parchment paper.
Heat the jam in a small saucepan or butter warmer (or at 20-second intervals in the microwave) until it is warm and more of a liquid consistency. Dilute with a tablespoon of warm water and mix well.
Using a pastry brush or a spoon, coat the pound cakes with two applications of the jam and allow it to soak in to the cake for about five minutes for each application. It should soak about 1/8 of an inch into the cake. After the second application has soaked in, pour the nonpareils into a dish at least 2 inches deep or tupperware and roll each cake until they are completely covered in the nonpareils. They should just be sticky enough to allow the nonpareils to stick to the cake, but you shouldn’t have any jam oozing. If they ooze, the cake needs to sit longer while the jam soaks in more.
These will keep for about 4 days and should be stored on a cake plate with a dome top or in an airtight container.