Add the raspberries and lemon juice to a food processor and blend until completely smooth. This lemon juice brightens the raspberry flavor and adds subtle complexity to the final ice cream. Pour the puree into a small bowl and set aside. You can strain it through a fine mesh sieve if you prefer a smoother texture without seeds, though I prefer leaving the seeds for authentic berry texture and mouthfeel.

In a large bowl, whip the heavy cream using an electric mixer on medium-high speed until stiff peaks form, about 2-3 minutes. This creates the airy, fluffy base that gives no-churn ice cream its luxurious texture. In a separate bowl, whisk together the sweetened condensed milk, crème fraîche, vanilla extract, and fine sea salt until well combined and smooth.

Gently fold the condensed milk mixture from Step 2 into the whipped cream using a spatula, being careful not to deflate the whipped cream—this folding technique preserves the air bubbles that create the ice cream's creamy texture. In a freezer-safe container (about 1.5-quart capacity), spread half of the cream mixture on the bottom. Drizzle half of the raspberry puree from Step 1 over the cream layer, then top with the remaining cream mixture and finish with the remaining puree.

Using a skewer, long knife, or toothpick, gently swirl through the layered mixture 6-8 times to create beautiful ripples and marble patterns throughout the ice cream—don't over-swirl or you'll lose the distinct layers. Cover the container with plastic wrap or a lid and place in the freezer for at least 4 hours, or preferably overnight for best texture and flavor development. I find the ice cream scoops beautifully after a full 24-hour freeze.