First, let cool a bit of sourdough with durum wheat semolina. Then, pull sourdough out of the fridge and bring it to room temperature, make a mix with 100 g and 100 g of regrinded wheat semolina and 50 ml of water.
Let rise at least until the doubling of the volume of the dough.
In a large bowl put the wheat flour and durum wheat semolina and mix the two flours, add the potatoes (boiled and mashed, better if prepared the day before), sourdough, water and salt, then knead vigorously in the bowl first and then on a pastry board until you obtain a homogeneous mixture.
Put the dough in the bowl and let rise for long enough to at least achieve twice the volume (typically 5 h). Without overworking the dough, divide it into three parts, put each of these in a round baking pan (classic form) well greased with olive oil, add more oil evenly over the dough and flatten into a baking dishby exerting pressure with your fingers in order to produce the characteristic holes.
Cut the tomatoes in half and put them in the dough with the cut part facing downwards. it is a feature of this focaccia, the fact that the tomatoes must be almost completely inserted into the dough. Sprinkle the focaccia with extra virgin olive oil and let rise again. It will be ready when the volume is nearly doubled (see procedure in the photo).
Sprinkle with oregano and bake in preheated oven at 230° C for about 30-40 minutes.
The times are indicative only because the rise (especially with sourdough) depends greatly on the temperature (and thus the season), and cooking depends on your oven.

The focaccia is a traditional product of Puglia. Anyone who has traveled in this region will certainly have seen people walking in the street with a nice slice of this focaccia in hand.
The resulting mixture is thick and very soft inside of which lie the tomatoes. Oregano (very abundant and used a lot in this region) makes it particularly fragrant and contributes to its organoleptic characterization.
This focaccia in Puglia is the ideal food for the morning snack, or it is consumed, especially in the summer evenings, during walks along the seafront.
Each city has its own recipe and its variant. Each uses a special ingredient to flavor it. Furthermore, even for the thickness and texture there would be several schools of thought, there are those who want high and soft and those who want to lower and crisp. The original recipe from Bari describe it pretty high and soft, you must be able to split in half. It is often eaten stuffed with mortadella.

A key feature of this focaccia pugliese is the use of durum wheat (excellent product from Puglia), and boiled potatoes that make the dough soft.

For each serving:
Energy: 349.34 Kcal
Total Dietary Fiber: 3.68 g
Alcohol: 0.00 g
Water: 111.38 g
Total Protein: 12.22 g
Animal protein: 0.00 g
Plant proteins: 12.22 g
Total lipids: 3.65 g
Lipids animals: 0.00 g
Plant lipids: 3.65 g
Cholesterol: 0.00 mg
Available carbohydrates: 71.30 g
Starch: 67.23 g
Sugars: 4.07 g