I found it interesting because the stem pierced through the center of the round shaped leaf & at the top there's a nice flower
Miner's lettuce, mostly gone to seed, in my back yard.
Purslane family- disk like leave that covers the stem.
Claytonia perfoliata (miner's lettuce, winter purslane, or Indian lettuce; syn. Montia perfoliata) is a fleshy annual plant native to the western mountain and coastal regions of North America from southernmost Alaska and central British Columbia south to Central America, but most common in California in the Sacramento and northern San Joaquin valleys.