Make the doughnuts: Add the first 6 doughnut ingredients to a large bowl and stir to combine.
Add the flour and salt and stir (or mix with your hands) until the dough comes together (it will still be wet and sticky).
On a well-floured surface, knead and shape the dough into a thick disk; transfer it to a bowl that's greased with oil or cooking spray and let it rest in a warm, draft-free area for 1 hour.
On a well-floured surface, flatten the dough and roll it out into a 1/4-inch-thick disk. Use a 2-inch round cookie cutter to cut out as many circles of dough as you can. Transfer the circles to a 10-by-15-inch baking sheet that's lined with parchment paper and greased with oil. Collect the dough trimmings and form them into another ball; roll it into another 1/4-inch-thick disk, cut out more doughnuts, and transfer them to the baking sheet. Repeat with the remaining dough.
Let the dough circles rest in a warm, draft-free area for 1/2 hour. Then heat about 1 inch of oil in a high-sided skillet over medium-high heat until very hot but not smoking (365 to 375 degrees F).
Working in batches, fry the doughnuts until they're golden brown on one side, then flip them and finish frying, about 3 minutes total. Transfer the doughnuts to a paper towel to drain.
Fill and finish: Transfer some of the Concord Grape Jelly to a pastry bag or to a zip-top bag with a small hole cut from one corner. When the doughnuts have cooled completely, use a small knife to gently burrow from the side of the doughnut to the center. Insert the tip of the bag into the opening and pipe in as much filling as possible. Repeat with the remaining doughnuts and filling. Dust the doughnuts generously with powdered sugar, and sprinkle each with a small pinch of coarse salt.
Combine the grapes, sugar, and water in a nonreactive pot. Bring the mixture to a simmer over medium-high heat and cook, stirring often, until the grapes have broken down, 6 to 8 minutes. Place the cardamom pods and citrus-zest-strips in a piece of cheesecloth and secure it with twine; add the cheesecloth bundle to the grape mixture. Cool to room temperature and transfer the pot to the refrigerator overnight. Meanwhile, place 4 to 6 spoons (regular dinner is fine) in the freezer (you'll use them to test the jelly at the end).
Press the chilled grape mixture through a coarse mesh strainer. Discard the seeds. Return the strained grape mixture to a clean nonreactive pot, along with the lemon juice. Bring the mixture to a simmer over medium-high heat and cook until it begins to look shiny, 10 to 15 minutes.
Test the jelly: Take one of the spoons from the freezer and place about 1/2 teaspoon of the grape mixture on it. Return the spoon to the freezer for 3 to 4 minutes. (Meanwhile, turn the heat to low and cover the pot so the mixture does not reduce further than necessary.) Remove the sample from the freezer and try spreading it; if it's not thick enough, uncover the pot, turn the heat back up to medium, and cook the grape mixture for another 5 minutes before testing a second sample using another frozen spoon. Continue this testing process until the jelly spreads smoothly. Let the jelly cool, then store it in the refrigerator.
Instead of using a thermometer to measure the oil temperature, you can test it by throwing in a cube of dry old bread. When it fries to golden brown in about a minute, the oil is the right temperature.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Noah Bernamoff, chef/owner of Mile End Delicatessen in New York City