Make the crust: Pulse the walnuts, pitted dates, 1/2 tablespoon coconut oil, and a heaping 1/4 teaspoon sea salt in a food processor until the mixture is coarse and holds together when pressed.
Line an 8 x 4-inch loaf pan with parchment paper leaving about 1 inch overhang on two sides, then press the crust mixture firmly into the bottom of the pan and freeze for at least 15 minutes.
Make the cashew cheesecake layer: Drain the soaked cashews and add them to a high-powered blender with 1/2 cup coconut milk, 1/4 cup maple syrup, 1/4 cup fresh lemon juice, 1 tablespoon lemon zest, 2 teaspoons vanilla, and 1/2 teaspoon sea salt.
Blend until completely smooth and creamy, about 1 minute, scraping down the sides as needed.
Pour the cashew filling over the chilled crust and smooth the top; freeze until the layer is completely firm, at least 2 hours.
Make the raspberry layer: In a blender, combine the mostly thawed raspberries, 1/2 teaspoon lemon juice, 2 tablespoons maple syrup, and 2 tablespoons chia seeds, then blend until smooth.
Pour the raspberry purée over the frozen cheesecake layer and spread evenly, then return to the freezer for 4 hours or overnight until fully set.
To serve: Remove the cheesecake from the freezer and let thaw at room temperature at least 20 minutes. Lift it from the pan using the parchment overhang, slice into 8 to 10 pieces with a sharp knife, and let individual slices sit 15–20 minutes to reach a creamy consistency before serving.