In a small saucepan over low heat stir together the raspberries and sugar. Cook until the raspberries pop and begin to soften; approximately 5 minutes. Place in refrigerator and cool for 1 hour. Run the raspberry mixture through a fine mesh sieve.

Whisk together the sweetened condensed milk, vanilla, and salt.

Beat the whipping cream with a mixer until stiff peaks form. Fold one cup of whipping cream into the sweetened condensed milk mixture. Now take that mixture and fold it into the rest of the whipping cream.

Pour one-third of the ice cream mixture into a 9 x 5-inch loaf pan. Spoon 1/3 of the raspberries over the top and swirl them in with a chopstick or the end of a wooden spoon. Pour another one-third of the ice cream mixture into the pan. Spoon another one-third of the raspberries over the top and swirl in a chopstick or the end of a wooden spoon. Repeat one more time.

Cover the ice cream directly with plastic wrap and place in the freezer for 4-5 hours.