High altitude makes cookies spread in the pan, cakes fall, and few baked goods turn out as they do at sea level. This twice-monthly column presents recipes and tips that make baking in the mountains successful.

A simple recipe is often as good as a complicated one and this tart proves it. The pat-in-the-pan crumb crust and the one-bowl lemon filling come together in almost no time. And if you add the blueberries, (they require 15 minutes at most), you get a creamy, smooth, citrusy tart with a crown of sweet berries, as delightful to look at as it is to eat. Clearly, great results from little effort. 

Lemons vary in the amount and potency of their juice. Sometimes it’s taken only 1/4 cup, other times up to 1/2 cup, for me to reach the level of flavor I want in the filling. So, in the recipe, I suggest you take a taste test when preparing it to determine how much you’ll need. 

Lemon-blueberry tart

Make in a 9 1/2 -inch metal tart pan with a removable bottom

Active time: 30 minutes, with optional topping  

Total time: 5 1/2 hours

Blueberry Topping, optional

• 1 1/4 cups fresh blueberries
• 1/4 cup granulated sugar, preferably superfine
• Pinch of table salt
• 1-2 tablespoons cornstarch
• 2 tablespoons lemon juice, water, or creme de cassis

Tart crust

• Your favorite cookie or cracker crust, commercial or homemade, prebaked and cooled, or
• 1 1/2 cups ground cinnamon graham crackers
• 2 tablespoons granulated sugar
• 4 tablespoons melted unsalted butter

Lemon filling

• One 14-ounce can sweetened condensed milk
• 1/4-1/2 cup freshly squeezed lemon juice
• 1 teaspoon vanilla paste or extract
• 1/4 cup sour cream
• 1 large egg
• 2 large egg yolks

Make the blueberry topping, if using: Place the blueberries in a saucepan, stir in the sugar and salt, and heat on the stovetop over low-medium heat, stirring often, until the berries soften and release their juices. In a small bowl, dissolve 1 tablespoon of the cornstarch in the lemon juice/water/creme de cassis; it will form a thick slurry. Turn up the heat to medium-high so the berries are at a very low boil (a higher boil may prohibit the cornstarch from acting as a thickener so avoid a more intense boil), add the cornstarch mixture, and stir until the mixture returns to a low boil and the juices thicken and coat the back of spoon. If needed, dissolve the second tablespoon of cornstarch in a tablespoon of water or crème de cassis, add this to the saucepan, and stir, again until the mixture reaches the desired consistency. It needs to be thick enough to sit on top of the lemon filling rather than sink into it. Taste, add more sugar if needed. Remove the pan from the heat and set it aside to cool. You may store the berry filling covered in the refrigerator for several hours and up to a day.

Make the tart crust: Preheat the oven to 350 degrees with a rack in the center position. Whisk the graham cracker crumbs and sugar until well combined. Blend in 3 tablespoons of the melted butter until equally distributed in the dry ingredients. Let the mixture rest a few minutes so the butter is fully absorbed, it will look like wet sand. Pinch some between your fingers. It should hold together, if it doesn’t add up to 1 more tablespoon of melted butter,  teaspoon at a time, until it does. Too much butter will make the crust hard and difficult to cut, so add no more than necessary. 

Bake the crust: Dump the graham cracker mixture into your pan (no need to grease it) and use your fingers to press it into the sides and the base, making it an even thickness in both places. Use the flat bottom of a measuring cup to help level and pack the base. Place the pan on a cookie sheet, move it to the oven, and bake until the crust is set, 7-12 minutes. Transfer the pan to a rack to cool. Leave the oven on. 

Make the lemon filling: Whisk the sweetened condensed milk, 1/4 cup of the lemon juice, vanilla and sour cream until blended. Test the lemon flavor now, before the raw eggs are added, to protect yourself from salmonella poisoning. If desired, increase the lemon juice by 1 tablespoon at a time until you reach a strength you like, keep in mind that the flavor will weaken once the egg yolks are added. One at a time, whisk in the egg and the egg yolks. The mixture should be smooth and thick. 

Assemble and bake the tart: Gently pour and level the lemon filling in the prebaked crust. Decoratively drizzle the blueberry filling over it. Slide the pan onto your cookie sheet and move it into the oven. Bake until the filling is set but the center still jiggles slightly when you shake the pan, 20-30 minutes, though times may vary, so determine doneness by the how the tart looks rather than the time.  

Cool, refrigerate, serve, and store: Cool the tart on a rack for an hour, then refrigerate it, lightly covered for 4 hours or a day. Cut and serve the tart chilled. Store it in the ‘fridge for up to 3 days.