Preheat and prepare the pan: Set your oven to 175°C (350°F) fan-forced. Line a 12-hole muffin tin with paper cases or grease each hole generously with butter. The pan should feel hot when you hold your hand 10cm above it after 10 minutes of preheating.

Mix the dry ingredients: In a large bowl, whisk together the almond flour, erythritol, baking powder, and salt until no clumps remain. The mixture should look uniform and pale cream in colour, with a fine, sandy texture when you rub it between your fingers.

Combine the wet ingredients: In a separate small bowl or jug, whisk the eggs, melted butter, yoghurt, and vanilla extract until the mixture is completely smooth and pale yellow, with no streaks of egg white visible. It should smell rich and buttery.

Fold together gently: Pour the wet ingredients into the dry ingredients and stir with a silicone spatula just until combined. The batter will be thick and slightly sticky — stop mixing as soon as you no longer see dry flour. Overmixing will make the muffins tough, and you'll notice the batter becoming greasy if you keep stirring.

Add the blueberries: Gently fold in the fresh blueberries and lemon zest (if using) with just four or five turns of the spatula. The berries should be evenly distributed but not crushed — you want to see whole blueberries suspended in the thick, golden batter.

Fill the muffin cups: Divide the batter evenly among the 12 muffin cases, filling each about three-quarters full. The batter should mound slightly above the rim but not overflow. I use a cookie scoop for uniform portions — each scoop should weigh about 45g.

Bake until golden: Place the tin on the middle rack and bake for 20-22 minutes. At 18 minutes, the tops should be domed and golden brown. Insert a skewer into the centre of a muffin — it should come out clean or with a few moist crumbs, not wet batter. The kitchen will smell like toasted nuts and sweet blueberries.

Cool completely before storing: Let the muffins cool in the tin for 5 minutes, then transfer them to a wire rack. They will feel fragile when warm but firm up as they cool. Wait at least 20 minutes before storing or freezing — any residual heat will create condensation and soggy tops.