Place seeds in a mixing bowl. Pour melted butter over seeds; stir to coat. Combine 1 teaspoon vanilla sugar (see Cook's Note), 1 teaspoon cinnamon, and 1/2 teaspoon white sugar in a small bowl; mix well. Stir in vanilla extract. Spread sugar mixture over seeds, stirring to coat evenly.
Spread seeds over a baking sheet in a single layer. Combine 1 teaspoon vanilla sugar and 1 teaspoon cinnamon in a small bowl; sprinkle over seeds.
Bake seeds in the preheated oven for 30 minutes. Remove baking sheet from oven, stir seeds, and spread evenly on baking sheet again. Combine 1 teaspoon vanilla sugar and 1 teaspoon cinnamon in small bowl and sprinkle over seeds. Return seeds to oven for 30 more minutes.
Remove seeds from oven. Sprinkle remaining 1/2 teaspoon vanilla sugar over seeds, and return to oven for 5 minutes. Remove from oven, pour into a serving bowl, and serve warm.