Put the weighed flour through a sifter or fine strainer onto a sheet of waxed paper. If measuring, sift more flour than you need onto waxed paper and spoon it lightly into a 1-cup dry measure to overflowing. Sweep off the excess with a straight edge and transfer to a medium bowl. Repeat this process twice more.
Set an oven rack to the lower third position and preheat the oven to 350 degrees. Butter or coat the loaf pans lightly with cooking spray and dust them with all-purpose flour or fine dry unseasoned breadcrumbs. Knock out excess flour or crumbs and set the pans aside.
The cold butter should be slightly softened. Cut each stick into 8 pats. Lay them out in a single layer on a plate and let them sit about 10 minutes at room temperature. When you press a finger into the butter, the impressions hould stay. Be sure the butter is not soft enough to spread.
Beat the butter with an electric mixer—hand-held or stand mixer—until smooth, about 1 minute. Scrape the bowl. Add the salt and baking powder and beat 1 minute more. Beat in the vanilla and scrape the bowl and beater.
With the machine running on medium speed, gradually add the sugar 1/4 cup at a time, taking about 2 minutes. Stop the machine and scrape the bowl and beater. Beat 4 minutes more on medium high speed. Scrape the bowl and beater. (This lengthy beating creates the bubbles that will expand during baking to give the cake its light texture).
Beat in the eggs one or two at a time, beating until well-incorporated and the batter is smooth. Stop to scrape the bowl and beater as necessary.
Sprinkle in about one third of the flour and beat it into the batter on low speed only until incorporated and the batter is smooth. Beat in half the cream on low speed. Repeat with half the remaining flour and the rest of the cream. Finally beat in the last of the flour until the batter is very smooth.
Divide the batter between the pans, about 26 ounces per pan. Smooth the tops with a rubber spatula, and place the pans in the oven. Bake for 60 to 75 minutes, until the loaves are well-browned and begin to pull away from the sides of the pans. Internal temperature of the cakes is about 200 degrees.
Set the pans on a cooling rack and let them stand for 30 minutes. Then tip the loaves out of their pans, stand the cakes upright on the rack, and cool them completely. Wrapped airtight, the loaves will stay fresh at room temperature for 4 to 5 days. The cakes may also be frozen for up to 2 months.