Paul preached this same Lord to the churches in his epistles.
Prior to the decease of Paul and the rest of the apostles, it was the Gospel.
The Tanakh, known to us as the first 5 books of the Bible, makes mention of it briefly...
When the Lord told Moses:
" ... I will make all my goodness pass before thee, and I will proclaim the name of the Lord before thee; and will be gracious to whom I will be gracious, and will shew mercy on whom I will shew mercy." ( Exodus 33:19 )
Which is the same as He told Paul to write to the Romans in Romans 9.
Are you confusing the doctrine of the sovereignty of God with the doctrine of the absolute sovereignty of God like you are confusing the Tanakh with the Torah? The Tanakh is the Hebrew Bible consisting of the Torah (the five books of Moses, the Nevi'im (the Books of the Prophets), and the Ketuvim (the “Writings” – the poetical books, the Megillot, or Scrolls (Song of Solomon, Ruth, Lamentations of Jeremiah, Ecclesiastes, and Esther), prophecy (Daniel), and history (Ezra, Nehemiah, and I and II Chronicles).
Paul was Jewish to the core. Hence, he most definitely did not believe in the doctrine of the absolute sovereignty of God. However, very careless reading of his writings has resulted in his being seriously misunderstood.
I have here in my study 276 commentaries on Romans (including many multivolume works and every exegetical commentary on the Greek text of Romans that has ever been published in English by a publishing house or a University), and numerous other works about the Book of Romans. Therefore, I have a fairly good idea of what Paul wrote to the church in Rome. But again, some careless readers seriously misunderstand the Book of Romans.