Pit the plums. Most varieties are not freestone, so to pit them, cut each plum in half through the stem end, shaving alongside the pit, and then cut the meat away from the sides of the pit. Cut the plums into pieces. If very ripe, they may fall apart, but don’t worry. You should have three to four cups (500 to 660 grams).

In a wide pot or skillet, cook the plums, sugar, butter, and lemon juice over medium-high heat, stirring occasionally to prevent sticking, and adjusting heat to prevent burning, until the mixture is glossy, thick, and reduced to about half the volume, 10 to 15 minutes.

Scrape onto a plate or sheet pan, spreading it out to cool rapidly. (The filling can be made ahead and refrigerated.)

Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius). Butter the bottom and sides of a 10-inch (25-centimeter) springform pan.

Separate the eggs, placing the whites in the sparkling clean bowl of an electric mixer and the yolks in a small bowl. Cover the whites and set aside.

Sift together the flour, baking powder, salt, and baking soda.

Using an electric mixer fitted with the paddle attachment on medium speed, or a bowl and a wooden spoon, beat the butter until creamy and light in color.

Add the sugar and beat until incorporated.

Add the egg yolks, one at a time, beating well after each addition, and beat in the vanilla.

Add the flour mixture in three batches alternating with the yogurt, beginning and ending with the flour mixture and mixing just until completely blended. The batter will be stiff.

Spread the batter in the prepared pan. Bake the cake until pale golden and a toothpick inserted into the center comes out barely clean, about 18 minutes. Remove from the oven and place on a wire rack (do not remove cake from pan). Adjust the oven rack to the upper third of the oven and raise the temperature to 375 degrees Fahrenheit (190 degrees Celsius). 

Fit the electric mixer with the whisk attachment and beat the egg whites on low speed until foamy.

On high speed, gradually add the sugar and beat until stiff peaks form.

With the cake still in the pan, spread the plum filling over the top of the cake.

Spoon meringue in large dollops over the filling, then spread and swirl it to cover the filling.

Sprinkle almonds evenly over the meringue.

Return the cake to the oven and bake until the meringue is golden and the almonds are lightly browned, about 15 minutes.

Transfer the cake to a wire rack and let cool completely.

Run a thin-bladed knife or spatula around the inside edge of the pan to loosen the cake sides, then unlatch and remove pan ring. If desired, use an offset spatula to loosen the cake from the pan bottom and slide it onto a serving platter.

Cut into wedges to serve. The torte can be made up to six hours ahead and held at room temperature until serving. Refrigerate any leftovers.