Preheat the oven to 350 degrees F. Line a muffin tin with paper liners.: As the oven warms you will feel a faint dry heat and hear the click of the element cycling, which signals the environment is stabilizing. Proper preheating ensures the cupcakes rise evenly, creating a tender top rather than a flat, dense result. A common mistake is placing batter into a cold oven, which leads to poor lift and longer bake time. Prepare your muffin tin with liners now so the batter can go straight in when mixed.
Wash the berries and remove the stems. Puree in a food processor or blender. You should have about 1 cup puree.: When you pulse the fresh strawberries you will notice a fragrant, sweet smell and a vivid red color. The puree should be smooth with no large chunks, which helps the batter incorporate evenly. If the puree feels watery, drain briefly to concentrate flavor. Avoid overprocessing to the point of foam, as excess air can affect texture.
Combine the butter (or oil) and maple syrup in a glass, heatproof measuring cup. Warm in 15-second increments in the microwave, stopping to stir, until the butter (or oil) is melted. Let cool slightly.: Warming these together creates a glossy mixture that blends easily with eggs and puree. You should feel the warmth and smell the syrup as they meld, but let the mixture cool enough so it is not hot to the touch. Too hot a mixture risks cooking the eggs when combined. Stirring between short bursts prevents pockets of overheated fat.
Stir in the vanilla, eggs, and strawberry puree.: As you combine these, you will hear a gentle thickening sound and see the mixture take on a uniform pink hue. The eggs add body and structure, while the puree brings fruity moisture. Mix just until smooth, avoiding vigorous beating which can incorporate too much air and create tunnels in the baked cupcakes. If you notice the mixture separating, whisk gently until emulsified.
Stir together the flour, baking powder, baking soda, and salt in a medium bowl.: The dry mixture should look even and pale, with no lumps of leavening. Whisking distributes the baking powder and soda so each cupcake rises consistently. A common oversight is adding flour that is lumpy, which leads to pockets of dry flour in the batter, so sift or whisk thoroughly for a homogenous mixture.
Stir the puree mixture into the flour mixture.: After adding the wet to the dry you will see the batter come together, with streaks of pink evening out into a soft, ribbon like texture. Stir gently until just combined, because overmixing develops gluten and yields a tougher crumb. A visual cue is when no dry flour streaks remain and the batter falls slowly from the spatula. If the batter looks curdled stop mixing and fold slowly to bring it together.
Fill the prepared liners with the batter to about 3/4 full. Bake for 20-22 minutes or until a cake tester inserted into the centers comes out clean. Let cool for 2-3 minutes in the pan, then remove and let cool completely on a wire rack.: While baking you will notice a subtle aroma of fruit and syrup and the tops will turn a light golden pink. The cupcakes are done when they spring back lightly and a tester is clean. Avoid opening the oven early, as that can cause them to sink. Letting them rest briefly in the pan helps them set, but transfer to a rack to prevent soggy bottoms from trapped steam.
Make the Strawberry Cream Cheese Frosting and pipe or spread onto cupcakes. Serve.: The frosting should be smooth, creamy, and slightly tangy, balancing the sweet cake. When piping you will feel gentle resistance in the bag and see a neat swirl form. If the frosting is too soft chill it briefly, and if too firm let it warm a bit to pipe cleanly. A typical error is frosting warm cupcakes, which melts the frosting, so ensure they are fully cool for best presentation.