In a large glass bowl, whisk together the pumpkin, brown sugar, 2 teaspoons vanilla, pumpkin pie spice, 1/2 teaspoon cinnamon, lemon extract, and salt until smooth. Cover and refrigerate until well chilled, about 1 hour. After the rest, stir in the heavy cream and whole milk until fully combined.

Set up the ice cream maker according to the manufacturer's manual. Turn it on and pour in the chilled pumpkin mixture through the opening. Churn until it reaches a soft-serve thickness, about 20 to 30 minutes. Scrape the ice cream into an airtight container and freeze overnight.

For best results, freeze the machine's bowl for at least 24 hours before churning, following the manufacturer's directions.

Line a large rimmed baking sheet with parchment paper. In a small bowl, mix the maple syrup, remaining 1 teaspoon vanilla, almond extract, tamari, and cayenne pepper; set aside.

Coat a large heavy skillet with nonstick cooking spray and set over medium-high heat. Add the chopped almonds and stir constantly until fragrant and lightly toasted, about 3 minutes. Pour the maple-umami mixture over the warm almonds and keep stirring until the syrup coats the nuts, about 2 minutes.

Scrape the candied almonds onto the prepared baking sheet in an even layer and let cool completely. While the nuts are still warm, sprinkle with the remaining 1/2 teaspoon cinnamon. Spoon the spicy umami almond crunch over scoops of pumpkin pie ice cream before serving.