
Using a vegetable peeler, remove the zest of 2 lemons and the tangerine in strips. Drop into a large heatproof bowl (or use a fireproof bowl if you plan to set the punch on fire) and combine with sugar. Muddle together with a muddler, pestle or the back of a wooden spoon. Let mixture sit for at least 3 hours to infuse (or infuse overnight).
Halve the tangerine and squeeze juice into a measuring cup. Halve lemons and squeeze lemon juice into the measuring cup to make 3/4 cup juice in total. (Save any unsqueezed lemon halves for another purpose.)
When ready to serve, bring 1 quart water to a boil. Pour rum and cognac into the bowl with the sugar and peels. If you want to flame the punch, do so now; see note below.
Add reserved citrus juice and boiling water and stir well. Grate nutmeg over top of punch and ladle into glasses.