Heat the oven to 350°F (175°C). Grease two 9-by-5-inch loaf pans. If you like, add parchment slings to help lift out the cooled loaves.
Beat the softened butter, cream cheese, and sugar in a large bowl until smooth and lighter in texture. Scrape down the bowl. Beat in the eggs one at a time, then mix in the vanilla.
In another bowl, whisk together the flour, cinnamon, baking soda, and salt. Add the dry mixture to the wet mixture in a few additions, mixing on low just until combined. Fold with a spatula to catch any flour at the bottom.
Divide the batter mentally into four equal portions. Spread one portion into each prepared pan, so half of the total batter remains in the bowl.
Spoon 1/4 cup of caramel over the batter in each pan, using all 1/2 cup between the two pans. Make a few shallow swirls with a skewer or knife, leaving a border of plain batter around the edges.
Divide the remaining batter evenly between the pans. Spoon it over the caramel and spread gently to cover it.
Bake on the center rack for about 45–50 minutes, with space between the pans. Begin checking at 45 minutes. A toothpick inserted into the cake near the center should come out without wet batter. If it lands in caramel, check a nearby spot. Loosely cover the tops with foil if they brown before the centers are ready.
Let the loaves cool in their pans on a rack for about 15 minutes. Carefully remove them from the pans and let them cool for about another 45 minutes before slicing.