In the beginning
Whether Genesis 1:1 is an independent declaration that God created everything, or a temporal clause introducing the state of the world when God began to create.
Genesis 1:1
1In the beginning, God created the heavens and the earth.
What each tradition says
Rabbinic / Midrashic
According to this source, the Prophets and many of the Psalms accept without reservation the doctrine of creation from nothing by the will of a supermundane personal God. The source presents this creation from nothing as their clear teaching.
Richard Gottheil, Emil G. Hirsch, et al., Creation (Jewish Encyclopedia, 1901-1906) — Creation, opening section (creation from nothing)
Patristic
Theophilus reports that the teachers he received taught with one consent that God made all things out of nothing. They held that nothing was coeval with God.
Theophilus of Antioch, Theophilus to Autolycus, Book II (Ante-Nicene Christian Library vol. 20, trans. Marcus Dods) — Book II, Chap. X — The world created by God through the Word
Catholic
Aquinas says things are said to be created in the beginning of time, not as if the beginning of time were a measure of creation. Rather, it is because together with time heaven and earth were created.
Thomas Aquinas, Summa Theologiae, Prima Pars (Fathers of the English Dominican Province trans.) — I q. 46, a. 3, Reply to Objection 1
Orthodox
Basil of Caesarea reads “In the beginning God created” as meaning “in the beginning of time.” He says the wise writer who tells of the birth of the Universe places these words at the head of the narrative.
Basil of Caesarea, The Hexaemeron (St. Basil: Letters and Select Works) — Homily I, on the words 'In the beginning'
Reformed / Protestant
Calvin contends that the world was made out of nothing, and he grounds this in the fact that it was created: because the world was created, it was made out of nothing. He notes that he has argued this point previously.
John Calvin, Commentaries on the First Book of Moses called Genesis, Vol. I (trans. John King, Calvin Translation Society, 1847) — Commentary on Genesis 1:20-21 (the word 'created': the world was made out of nothing)
Evangelical
In commenting on Genesis 1:1, Matthew Henry says that when this work was produced, it was like a clock first set going. Time began with the production of those beings that are measured by time.
Matthew Henry, An Exposition of the Old and New Testament (Vol. I, 1853 ed.) — Commentary on Genesis 1:1, section 4 ('When this work was produced')