Step 1

Bring raspberries, sugar, and ¼ tsp. salt to a simmer in a medium saucepan over medium heat and cook, stirring often, until raspberries begin to burst and lose their shape, about 4 minutes. Strain through a fine-mesh sieve into a large measuring glass, pressing on solids; discard solids. Pour back into saucepan and return to medium heat. Cook, stirring occasionally, until sauce is thick enough to coat a spoon, 10–15 minutes. (You should have about 6 Tbsp.) Transfer back to measuring glass and chill until cold, about 30 minutes.

Step 2

Mix condensed milk, almond extract, and remaining ¾ tsp. salt in a medium bowl to combine.

Step 3

Using an electric mixer, beat cream in a medium bowl, starting on low speed and gradually increasing to medium-high as it thickens, until billowy and stiff peaks form, about 4 minutes.

Step 4

Add a dollop of whipped cream to condensed milk mixture and mix in with a rubber spatula (this is just to lighten it so that the next stage—folding—is easier). Add remaining whipped cream; fold in, running spatula down sides and along bottom of bowl, then lifting up through center and over top while rotating bowl to integrate without deflating, until very few streaks of condensed milk mixture remain.

Step 5

Scrape about one third of ice cream base into a loaf pan that’s at least 8½x4½". Drizzle over one third of raspberry syrup. Repeat layers 2 more times, ending with raspberry syrup (no need to be precise). Using a small offset spatula or butter knife, make figure-eight motions through ice cream base to swirl raspberry syrup throughout. Cover with plastic wrap or an airtight silicone lid and freeze until solid, at least 8 hours.

Step 6

To serve, transfer loaf pan to refrigerator and let ice cream soften 10 minutes before scooping into bowls.

Step 7

Do Ahead: Ice cream can be made 1 week ahead. Keep frozen.