Preheat oven to 425 degrees. Spray 2 4-inch ramekins (that hold about 6-8 oz) with non-stick spray and lightly dust/coat with cocoa powder. Line the bottoms with parchment rounds if desired.
Add the chocolate and butter to a microwave safe bowl. Heat at 50% power for 1 minute. Stir well then heat at 50% power for 30 seconds then stir. Continue to heat at 50% power for 20 second intervals, stirring well each time, until the chocolate is melted. Set aside.
Add the egg, egg yolk, granulated sugar, and salt to a medium bowl. Use a hand mixer to beat on high speed until light in color and slightly thickened and pale.
While the mixer is running on medium, pour in 1/2 of the melted chocolate and mix to combine. Turn off the mixer and add the remaining chocolate. Beat until smooth.
Add the gluten free flour and use a spatula to fold into the chocolate mixture until just combined.
Transfer the batter equally among the two prepared ramekins. Bake at 425 degrees for 12-14 minutes. When done, the edges will be set and the middle will be soft and jiggly.
When done, cool in the ramekins for 1 minute. Then invert onto a plate and let sit for 10-15 seconds before removing the ramekin.
Serve immediately with vanilla ice cream or whipped cream.