Preheat oven to 300° Fahrenheit. Place 6 crème brûlée ramekin dishes in a baking dish or two; set aside.
In a 4 cup or larger measuring cut (you can use a bowl, but it's easier in a measuring cup because you'll be pouring it out later), whisk together the egg yolks, zest, extracts, and food coloring. Set aside.
In a small saucepan, heat the cream, milk, sweetener, and salt over medium-high heat, stirring occasionally to prevent scorching, until just beginning to bubble.
Remove the cream mixture from the heat and slowly pour into the egg mixture with one hand while briskly whisking with your other hand.
Pour the liquid into the ramekins until about ¾ full.
Pour cold water into thebaking dish around the ramekins so the water rises about halway up the ramekin dishes.
Pop into the oven and bake for 30 to 40 minutes (give or take, varies based on size, shape, and depth of ramekins) or until mostly set. The center should still be a bit jiggly.
Using a spatula, carefully remove the ramekins from the water and set on a cooling rack.
Cool for about 20 minutes then cover with plastic wrap (be careful not to touch the surface of the custard) and refrigerate for 3 or more hours.
Sprinkle ½ to 1 teaspoon erythritol over thetop of each chilled crème brûlée. Melt and caramelize this sweetener with a torch until golden brown.
Allow to cool an additional 10 or so minutes so the caramelization can harden into a crust.
Garnish with lemon slices or strawberries if desired.