Step 1In a medium bowl, stir together the sugar and butter until completely combined and smooth. Stir in the oats until they are coated and the topping forms clumps. Spread the topping onto a rimmed baking sheet and refrigerate until chilled and hardened. Break up the clumps and store, refrigerated, in a sealable plastic bag. This makes slightly more topping than is needed for the muffins; the topping will keep, refrigerated, up to 1 month (or frozen up to 3 months).
Step 1Heat the oven to 375 degrees. Lightly grease the muffin tins to prepare them.
Step 2In a medium bowl, combine the oats and buttermilk, and set aside so the oats can soak.
Step 3Meanwhile, in the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl using a hand mixer, beat together the oil, eggs and vanilla.
Step 4In a separate bowl, whisk together the oat bran, flax meal, cornmeal, sugar, poppy seeds, baking powder and soda, and salt.
Step 5Add the soaked oats and buttermilk to the bowl with the egg mixture, then, with the mixer running, slowly incorporate the dry ingredients. Fold in the dried cherries.
Step 6Spoon the batter into the muffin tins, filling each cup approximately two-thirds of the way full. Top each muffin with a light crumbling of streusel topping.
Step 7Bake the muffins until puffed and a rich golden coloring on top, and a toothpick inserted comes out clean, 22 to 26 minutes, rotating each tray halfway through.
Step 8Cool the muffins on a rack before unmolding.