Preheat the oven to 350°F. Line a 9×5 inch bread pan with parchment paper.In a bowl, whisk together the melted butter, brown sugar, yogurt, eggs, and vanilla. Add the flour, baking powder, and salt. Mix until fully combined. Mix the peaches into the batter. Pour the batter into the prepared pan. Swirl in the peach jam, leaving streaks of jam throughout the batter.To make the cinnamon swirl. Mix the butter, brown sugar, flour, and cinnamon. Arrange the clumps over the batter. Bake for 55-60 minutes or until the center is just set. If the loaf is browning too quickly, cover with foil. Remove, slice, and enjoy with butter and flaked sea salt.