Pre-heat oven to 425 degrees.
Place cherries on a foil-lined baking sheet and put in the upper rack of the oven for 15 minutes, until cherries are starting to shrivel. On the lower rack of the oven, place a 12-inch oven-proof skillet, so it can heat up while you prepare the clafoutis.
Place roasted cherries in a medium bowl and sprinkle with lemon juice. Let cool for about 5 minutes. Combine cinnamon and 2 tsp flour together and toss mixture over the cherries.
While cherries are roasting, in a large bowl, combine eggs, sugar, vanilla extract, and salt and whisk until sugar is mostly dissolved. Add ½ cup flour and whisk until well combined.
Add heavy cream and whole milk to the bowl and whisk until smooth.
Remove skillet from oven and melt butter in it, making sure to coat entire skillet. Pour custard mixture into skillet and sprinkle cherries all around.
Place skillet back in oven for 18-22 minutes until clafoutis is browning and has an internal temperature of 195 degrees.
Let clafoutis rest for about 25 minutes before sprinkling with confectioners' or granulated sugar (confectioners' is prettier, but granulated has a better texture).