Preheat your waffle iron to medium-high heat and set your oven to 200°F with a baking sheet inside—this will keep your finished waffles warm and crispy while you cook the remaining batches. Bring your eggs and milk to room temperature if they aren't already, as this helps create a more uniform batter. Lightly chop or crush the raspberries with a fork, breaking them into smaller pieces so they distribute evenly throughout the waffles without creating overly large pockets.

In a medium bowl, whisk together the flour, baking powder, cinnamon, and salt. This distributes the leavening and spices evenly throughout the dry mixture, ensuring consistent flavor and rise in every waffle. Don't skip the whisking step—it aerates the flour and prevents lumps in your final batter.

In a second bowl, whisk together the melted butter (make sure it's cooled slightly), eggs, vanilla extract, sugar, and milk until well combined. The mixture should be smooth and uniform—this creates a cohesive wet base that will bind with your dry ingredients. I like to add the sugar here with the wet ingredients rather than the dry mix, as it dissolves better and creates a slightly more tender waffle.

Pour the wet ingredient mixture from Step 3 into the dry ingredient mixture from Step 2, stirring gently until just combined—the batter should be slightly lumpy, not smooth. Overmixing develops gluten and leads to tough, dense waffles. Gently fold in the prepared raspberries from Step 1 using a spatula, being careful not to crush them further or overmix the batter.

Lightly butter or oil your preheated waffle iron and pour about 3/4 cup of batter (adjust based on your waffle iron size) onto the center of the grid. Close the lid and cook until the waffle is golden brown and crispy, usually 3-5 minutes depending on your iron. Most waffle irons have an indicator light that signals when they're done, but I rely on the aroma and color as my guide. Transfer each finished waffle to the warm baking sheet in the 200°F oven to keep it warm while you cook the remaining batches.

Remove waffles from the oven and arrange on serving plates while they're still warm. Top with your favorite accompaniments such as whipped cream, fresh berries, maple syrup, or a dusting of powdered sugar. Serve immediately for the best texture and flavor.