In a large Mixing Bowl, whisk together the 1 ¼ cups harina de trigo, 3 tbsp azúcar en polvo cernida, and ¼ tsp sal. Add the cold 8 tbsp mantequilla sin sal fría, cortada en cubos pequeños cubes and use your fingertips to rub the 8 tbsp mantequilla sin sal fría, cortada en cubos pequeños into the 1 ¼ cups harina de trigo until the mixture resembles coarse, pea-sized crumbs.

Add the 1 yema de huevo and 2 tablespoons of 2 tbsp agua helada más. Mix with a fork, then use your hands to gently bring the dough together. Add an extra teaspoon of 2 tbsp agua helada más at a time only if the dough is too dry to hold together. Do not overwork it.

Shape the dough into a flat disc, wrap it tightly in Plastic Wrap, and refrigerate for at least 30 minutes (or up to 2 days).

Preheat your Oven to 375°F. On a lightly 1 ¼ cups harina de trigo-dusted surface, roll the chilled dough into a circle about 11–12 inches in diameter and roughly 1/8-inch thick. Work quickly to keep the dough cold.

Carefully drape the dough over your Rolling Pin and transfer it into a Tart Pan with a removable bottom. Gently press the dough into the corners and up the sides. Roll the pin over the top of the pan to trim off any excess dough.

Prick the bottom of the crust all over with a fork (this is called docking). Line the crust with a sheet of Parchment Paper and fill it with pie weights or dried beans. Place the Tart Pan on a Baking Sheet.

Blind bake the crust for 15 minutes. Carefully remove the Parchment Paper and pie weights, then bake for another 10–12 minutes until the crust is golden brown all over. Let it cool completely on a Wire Rack before filling.

In a medium Saucepan, heat the 2 cups leche entera over medium heat until it just begins to steam and small bubbles form around the edges. Do not boil. Remove from heat and stir in the 1 tsp extracto de vainilla puro.

In a Mixing Bowl, whisk together the 1 yema de huevo, ⅓ cup azúcar granulada, and 3 tbsp almidón de maíz until the mixture is pale yellow and smooth, about 1–2 minutes.

Slowly pour about half of the hot 2 cups leche entera into the 1 yema de huevo mixture, whisking constantly to temper the eggs. Then pour the tempered mixture back into the Saucepan with the remaining 2 cups leche entera.

Cook over medium heat, whisking constantly, until the mixture thickens and large bubbles begin to pop on the surface, about 3–4 minutes. Once it bubbles, cook for 1 more minute to fully cook out the 3 tbsp almidón de maíz.

Remove from heat and whisk in the 8 tbsp mantequilla sin sal fría, cortada en cubos pequeños pieces until fully melted and incorporated. Pour the pastry cream through a fine-mesh Sieve into a clean Mixing Bowl to remove any lumps.

Press a sheet of Plastic Wrap directly onto the surface of the pastry cream (this prevents a skin from forming). Refrigerate until completely cold and set, at least 1 hour.

In a small Saucepan, combine the 18 oz frambuesas frescas aproximadamente 3 tazas, enjuagadas y secadas and 2 tbsp agua helada más over low heat. Stir until the 18 oz frambuesas frescas aproximadamente 3 tazas, enjuagadas y secadas is melted and smooth. Remove from heat and let cool slightly until it's still fluid but not hot.

Once the pastry cream is fully chilled, whisk it briefly to loosen it, then spoon it into the cooled tart shell. Use an Spatula to spread it into an even, smooth layer.

Arrange the fresh 18 oz frambuesas frescas aproximadamente 3 tazas, enjuagadas y secadas over the pastry cream in concentric circles, starting from the outer edge and working inward. Place each berry open-side down for the most attractive presentation.

Using a Pastry Brush, gently brush the warm 18 oz frambuesas frescas aproximadamente 3 tazas, enjuagadas y secadas glaze over all the 18 oz frambuesas frescas aproximadamente 3 tazas, enjuagadas y secadas to give them a beautiful, glossy shine. Be gentle so you don't disturb the berries.

Refrigerate the finished tart for at least 20 minutes to allow everything to set before slicing. Dust with a little 3 tbsp azúcar en polvo cernida just before serving if desired. Remove the tart ring, slice, and serve chilled.